Input Methods for Mobile Devices

ABSTRACT

This document describes techniques and systems that enable input methods for mobile devices. A radar field enables an electronic device to accurately determine that a part of a user is within a gesture zone around the device. Further, the device can determine whether an application configured to receive input through radar-based gestures (radar gestures) is operating on the device. Using these techniques, the device can present a feedback indicator on a display when the user&#39;s hand is within a gesture zone around the device. The feedback indicator alerts the user that the user&#39;s hand is close enough to the device to make specific radar gestures. This allows the device to provide the user with feedback, which can educate the user about the device&#39;s capabilities and allow the user to take advantage of additional functionality and features provided by the availability of the radar gestures.

RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/US2019/049204, filed Aug. 30, 2019, and titled“Input Methods for Mobile Devices,” the disclosure of which isincorporated in its entirety by reference herein.

BACKGROUND

Electronic devices such as smartphones, wearable computers, and tablets,are powerful tools that are regularly relied upon for both business andpersonal use. The processing power of these devices is augmented bymachine learning that helps the devices anticipate their users'preferences. For all this computing power and artificial intelligence,however, these devices are still reactive communicators. That is,however “smart” a smartphone is, and however much the user talks to itlike it is a person, the electronic device is still dependent on beingactivated before it can provide feedback. To activate the mobile device,the user typically has to first pick up the device to make it aware ofthe user's intention to use the electronic device. Only after thisphysical interaction can the device make applications and functionalityavailable for the user. Consequently, many electronic devices providepoor user experiences prior to explicit interaction by the user.

SUMMARY

This document describes techniques and systems that enable input methodsfor mobile devices. The techniques and systems use a radar field toenable an electronic device to accurately determine the presence orabsence of a user near the electronic device. Further, the electronicdevice can determine whether an application that can receive inputthrough radar-based touch-independent gestures (radar gestures) isoperating on the electronic device. Using these techniques, theelectronic device presents a feedback indicator when the user's hand iswithin a gesture zone around the electronic device. The feedbackindicator lets the user know, when radar-gesture input is generallyavailable for interacting with the electronic device, that the user'shand is close enough to the electronic device to make specific radargestures. This allows the device to provide the user with feedback,which can educate the user about what the electronic device is capableof and allow the user to take advantage of the additional functionalityand features provided by the availability of the radar gesture.

Aspects described below include a method implemented in an electronicdevice that includes a display and a radar system. The method comprisesdetermining, based on radar data received through the radar system, thata portion of a user is within a gesture zone of the electronic device.The method also includes determining that an application operating onthe electronic device is configured to receive radar-gesture input. Themethod further includes, in response to the determination that theportion of the user is within the gesture zone of the electronic deviceand the determination that the application operating on the electronicdevice is configured to receive radar-gesture input, providing afeedback indicator on the display of the electronic device. Theproviding of the feedback indicator indicates that the portion of theuser is within the gesture zone and that the application can receiveradar-gesture input.

Aspects described below also include an electronic device comprising adisplay, a radar system, a computer processor, and a computer-readablemedia. The radar system is implemented at least partially in hardwareand provides a radar field. The radar system also senses reflectionsfrom a user in the radar field, analyzes the reflections from the userin the radar field, and provides radar data based on the analysis of thereflections. The computer-readable media includes stored instructionsthat can be executed by the computer processor to implement aradar-based interaction manager. The radar-based interaction managerdetermines that an application operating on the electronic device isconfigured to receive radar-gesture input. The radar-based interactionmanager also determines, based on the radar data, that a portion of theuser is within a gesture zone of the electronic device. In response tothe determination that the application operating on the electronicdevice is configured to receive radar-gesture input and thedetermination that the portion of the user is within the gesture zone ofthe electronic device, the radar-based interaction manager causes thedisplay to present a feedback indicator, the presentation of thefeedback indicator indicating that the portion of the user is within thegesture zone and that the application can receive the radar-gestureinput.

Aspects described below include a system comprising a display, and anelectronic device that includes, or is associated with means forproviding a radar field that provides radar data, the radar data basedon sensing and analyzing reflections from an object in the radar field.The system also includes means for determining that an applicationoperating on the electronic device is configured to receiveradar-gesture input. The system also includes means for determining,based on the radar data, that a portion of the user is within a gesturezone of the electronic device. The system further includes means forpresenting, in response to determining that the application operating onthe electronic device is configured to receive radar-gesture input andthat the portion of the user is within the gesture zone of theelectronic device, a feedback indicator on the display of the electronicdevice, the presentation of the feedback indicator indicating that theportion of the user is within the gesture zone and that the applicationcan receive the radar-gesture input.

This summary is provided to introduce simplified concepts concerning theinput methods for mobile devices, which is further described below inthe Detailed Description and Drawings. This summary is not intended toidentify essential features of the claimed subject matter, nor is itintended for use in determining the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The details of one or more aspects of input methods for mobile devicesare described in this document with reference to the following drawings.The same numbers are used throughout the drawings to reference likefeatures and components:

FIG. 1 illustrates an example environment in which techniques enablingthe input methods for mobile devices can be implemented.

FIG. 2 illustrates an example implementation of an electronic device,including a radar system, that can implement the input methods formobile devices.

FIG. 3 illustrates an example implementation of the radar system ofFIGS. 1 and 2.

FIG. 4 illustrates example arrangements of receiving antenna elementsfor the radar system of FIG. 3.

FIG. 5 illustrates additional details of an example implementation ofthe radar system of FIGS. 1 and 2.

FIG. 6 illustrates an example scheme that can be implemented by theradar system of FIGS. 1 and 2.

FIG. 7 depicts an example method that enables the input methods formobile devices.

FIGS. 8-12 illustrate visual elements, including the feedback indicator,which can be presented on the display of the electronic device of FIGS.1 and 2 when a radar-gesture application is running on the electronicdevice.

FIGS. 13-15 illustrate the electronic device of FIGS. 1 and 2 operatingin multiple modes with examples of the visual elements that can bepresented on the display in the different modes.

FIG. 16 illustrates an example computing system that can be implementedas any type of client, server, and/or electronic device as describedwith reference to FIGS. 1-15 to implement, or in which techniques may beimplemented that enable, the input methods for mobile devices.

DETAILED DESCRIPTION

Overview

This document describes techniques and systems that enable input methodsfor mobile devices. The described techniques employ a radar system thatdetermines the user's presence (or absence) and location relative to theelectronic device. The techniques also determine when the device isrunning an application that can receive input through radar-basedtouch-independent gestures. When the device is running one of theseapplications and a user is present, the techniques provide a feedbackindicator, giving the user feedback that radar gestures can be receivedand are effective to control an application operating on the electronicdevice.

In this description, the terms “radar-based touch-independent gesture,”“3D gesture,” or “radar gesture” refer to the nature of a gesture inspace, away from the electronic device (e.g., the gesture does notrequire the user to touch the device, though the gesture does notpreclude touch). The radar gesture itself may often only have an activeinformational component that lies in two dimensions, such as a radargesture consisting of an upper-left-to-lower-right swipe in a plane, butbecause the radar gesture also has a distance from the electronic device(a “third” dimension), the radar gestures discussed herein can begenerally be considered three-dimensional.

Using these techniques, the electronic device can provide feedback and anotification to make the user aware of the available radar-gesture inputmode and, in some cases, provide feedback regarding the use and resultsof the radar gestures. A determination of the user's absence, presence,and location can also be used to provide a more-responsive andmore-efficient authentication process. For example, the techniquesenable the device to anticipate when the user is ready to beauthenticated and to more-accurately determine when to lock the devicewhen the user is away. Because the described techniques allow theelectronic device to provide the user with useful feedback aboutavailable input modes, interactions may be more convenient and lessfrustrating because the user is aware of the input modes and can beconfident about different ways in which the device can interact andreceive input.

Consider an example smartphone that includes the described radar system.In this example, an application that has a capability to receive inputthrough radar gestures is operating on the electronic device. This typeof application will be referred to as a radar-gesture-subscribedapplication (“radar-gesture application”). Examples of radar-gestureapplications include music players, media players, and applications orfeatures of an electronic device that provide alerts or a reminder, suchas a calendar. An interaction manager causes the electronic device topresent a feedback indicator on a display of the device when the user'shand is within a gesture zone around the electronic device. The gesturezone is a volume around the electronic device within which theradar-gesture can be detected by the radar system. For example, theinteraction manager can use radar data to determine that the user's handis within a threshold distance (e.g., the gesture zone) from theelectronic device. The threshold distance can be any suitable distancewithin which the radar system can recognize the user's hand, such aswithin three, five, seven, or nine inches. In some cases, the gesturezone may extend different threshold distances from the electronic devicein different directions (e.g., it can have a wedged, oblong, ellipsoid,or asymmetrical shape). The size or shape of the gesture zone can alsovary over time or be based on other factors such as a state of theelectronic device (e.g., battery level, orientation, locked orunlocked), or an environment (such as in a pocket or purse, in a car, oron a flat surface). Further, the gesture zone can have multiplesub-zones that correspond to different feedback indicators. For example,a primary feedback indicator can be presented when the user enters theouter limit of the gesture zone. Then as the user (e.g., the user'shand) gets closer to the electronic device, then a property of thefeedback indicator can change (e.g., it gets brighter, less or moretransparent, changes color, changes size or shape). When the userwithdraws, the feedback indicator can change in an inverse order.

The feedback indicator is a user-perceivable element, such as a visualelement that is presented on the display of the electronic device thatindicates that the user's hand is within the gesture zone. This informsthe user that radar gestures can be used to interact with aradar-gesture application. For example, when a radar-gesture applicationis running on the electronic device, the display may present an icon, acontrasted lighting area (e.g., an area that is brighter or dimmer thanthe surrounding area), or an area of different or contrasting color. Insome cases, the feedback indicator may be a combination of one or moreof these features. Thus, in this example, when the electronic devicedetermines that a radar-gesture application is running while the user'shand is in the gesture zone, an illuminated line appears at or near thetop edge of the display. In some implementations, this indicator canmove in some relationship with movements by the user or otherwisedynamically alter its appearance to approximately represent movements ofthe user's hand within the gesture zone.

Additionally, the amount and kind of radar gestures may vary atdifferent distances from the electronic device. For example, a gesturethat dismisses an alarm or silences a ringer, such as a “swipe” gesture(left-to-right, right-to-left, or up and down), may be available at aparticular distance, such as three to five feet. At closer distances(e.g., seven, nine, or twelve inches), more-detailed fine-motiongestures may be available, such as rubbing two fingers together toadjust a volume or brightness in small increments. The feedbackindicator can provide information regarding these differences, as well.For example, in the described example, the feedback indicator may besmaller, less bright, or have a different color when only the “swipe”gesture is available (at around three feet from the electronic device).But, at the close distance, when more or different gestures areavailable, the feedback indicator can enlarge, brighten, or become adifferent color.

The described techniques and systems employ a radar system, along withother features, to provide a useful and rewarding user experience thatchanges based on the user's presence or absence and the operation of aradar-gesture application on the electronic device. Rather than relyingonly on the user's knowledge and explicit user input, the electronicdevice can provide feedback to the user to indicate that the device isaware of the user's location and alert the user to the features andfunctionality that are available.

Some conventional electronic devices may include sensors, such ascameras, proximity sensors (e.g., capacitive or infra-red sensors), oraccelerometers to determine the location of the user and adjust variousfunctions of the electronic device based on the proximity of the user.For example, the electronic device may provide additional privacy oraesthetic value by turning off a display unless the user is within apredetermined distance. The conventional electronic device, however,typically cannot provide a useful and rich ambient experience that caneducate the user about the capabilities of the electronic device. Theseare but a few examples of how the described techniques and devices maybe used to enable input methods for mobile devices, other examples andimplementations of which are described throughout this document. Thedocument now turns to an example operating environment, after whichexample devices, methods, and systems are described.

Operating Environment

FIG. 1 illustrates an example environment 100 in which techniquesenabling input methods for mobile devices can be implemented. Theexample environment 100 includes an electronic device 102, whichincludes, or is associated with, a radar system 104, a persistentradar-based interaction manager 106 (interaction manager 106), and,optionally, one or more non-radar sensors 108 (non-radar sensor 108).The term “persistent,” with reference to the radar system 104 or theinteraction manager 106, means that no user interaction is required toactivate the radar system 104 (which may operate in various modes, suchas a dormant mode, an engaged mode, or an active mode) or theinteraction manager 106. In some implementations, the “persistent” statemay be paused or turned off (e.g., by a user). In other implementations,the “persistent” state may be scheduled or otherwise managed inaccordance with one or more parameters of the electronic device 102 (oranother electronic device). For example, the user may schedule the“persistent” state such that it is only operational during daylighthours, even though the electronic device 102 is on both at night andduring the day. The non-radar sensor 108 can be any of a variety ofdevices, such as an audio sensor (e.g., a microphone), a touch-inputsensor (e.g., a touchscreen), or an image-capture device (e.g., a cameraor video-camera).

In the example environment 100, the radar system 104 provides a radarfield 110 by transmitting one or more radar signals or waveforms asdescribed below with reference to FIGS. 3-6. The radar field 110 is avolume of space from which the radar system 104 can detect reflectionsof the radar signals and waveforms (e.g., radar signals and waveformsreflected from objects in the volume of space). The radar field 110 maybe configured in multiple shapes, such as a sphere, a hemisphere, anellipsoid, a cone, one or more lobes, or an asymmetric shape (e.g., thatcan cover an area on either side of an obstruction that is notpenetrable by radar). The radar system 104 also enables the electronicdevice 102, or another electronic device, to sense and analyzereflections from an object in the radar field 110. The radar field 110may be used to provide a recognition zone. The recognition zone is avolume around the radar system 104 that may extend any of a variety ofdistances from the radar system 104, such as approximately three, seven,ten, or fourteen feet (or approximately one, two, three, or fourmeters). The recognition zone may be the same or less than a maximumextent of the radar field 110. The recognition zone may be a static sizeor shape that is predefined, user-selectable, or determined via anothermethod (e.g., based on power requirements, remaining battery life, oranother factor). In some cases, the recognition zone may be dynamicallyand automatically adjustable by the interaction manager 106 based onvarious factors, such as the velocity or location of the electronicdevice 102, a time of day, or a state of an application running on theelectronic device 102. The threshold distance of the recognition zonecan be determined based on a number of relevant factors, such as batterylevel, location of the electronic device, velocity of the electronicdevice, or data received from one or more of the radar system, othersensors, or applications running on the electronic device.

Some implementations of the radar system 104 are particularlyadvantageous as applied in the context of smartphones, such as theelectronic device 102, for which there is a convergence of issues suchas a need for low power, a need for processing efficiency, limitationsin a spacing and layout of antenna elements, and other issues, and areeven further advantageous in the particular context of smartphones forwhich radar detection of fine hand gestures is desired. Although theimplementations are particularly advantageous in the described contextof the smartphone for which fine radar-detected hand gestures arerequired, it is to be appreciated that the applicability of the featuresand advantages of the present invention is not necessarily so limited,and other implementations involving other types of electronic devices(e.g., as described with reference to FIG. 2) are also within the scopeof the present teachings.

The object may be any of a variety of objects from which the radarsystem 104 can sense and analyze radar reflections, such as wood,plastic, metal, fabric, a human body, or human body parts (e.g., a foot,hand, or finger of a user of the electronic device 102). As shown inFIG. 1, the object is a hand 112 of a user of the electronic device 102.Based on the analysis of the reflections, the radar system 104 canprovide radar data that includes various types of information associatedwith the radar field 110 and the reflections from the hand 112, asdescribed with reference to FIGS. 3-6 (e.g., the radar system 104 canpass the radar data to other entities, such as the interaction manager106).

The radar data can be continuously or periodically provided over time,based on the sensed and analyzed reflections from the object (e.g., thehand 112 in the radar field 110). A position of the hand 112 can changeover time (e.g., the hand 112 may move within the radar field 110) andthe radar data can thus vary over time corresponding to the changedpositions, reflections, and analyses. Because the radar data may varyover time, the radar system 104 provides radar data that includes one ormore subsets of radar data that correspond to different periods of time.For example, the radar system 104 can provide a first subset of theradar data corresponding to a first time-period, a second subset of theradar data corresponding to a second time-period, and so forth. In somecases, different subsets of the radar data may overlap, entirely or inpart (e.g., one subset of the radar data may include some or all of thesame data as another subset).

The electronic device 102 can also include a display 114 and anapplication manager 116. The display 114 can include any suitabledisplay device, such as a touchscreen, a liquid crystal display (LCD),thin film transistor (TFT) LCD, an in-place switching (IPS) LCD, acapacitive touchscreen display, an organic light emitting diode (OLED)display, an active-matrix organic light-emitting diode (AMOLED) display,super AMOLED display, and so forth. The display 114 is used to displayvisual elements that are associated with various modes of the electronicdevice 102, which are described in further detail herein with referenceto FIGS. 10-15. The application manager 116 can communicate and interactwith applications operating on the electronic device 102 to determineand resolve conflicts between applications (e.g., processor resourceusage, power usage, or access to other components of the electronicdevice 102). The application manager 116 can also interact withapplications to determine the applications' available input modes, suchas touch, voice, or radar gestures, and communicate the available modesto the interaction manager 106.

The interaction manager 106 can be used to interact with or controlvarious components of the electronic device 102 (e.g., modules,managers, systems, interfaces, or one or more of the non-radar sensors108). For instance, the interaction manager 106 (independently orthrough the application manager 116) can determine that an applicationoperating on the electronic device has a capability to receiveradar-gesture input (e.g., a radar-gesture application). Theradar-gesture input may be based on the radar data and received throughthe radar system 104. The interaction manager 106, or the radar system104, can also use one or more subsets of the radar data to determinethat a portion of the user, such as the hand 112, is within a gesturezone 118 of the electronic device 102. The gesture zone 118 is a regionor volume around the electronic device 102 within which the radar system104 (or another module or application) can detect radar gestures anddetermine the action associated with the radar gesture. For example, theinteraction manager 106 can detect a user's reach toward the electronicdevice 102. To do this, the interaction manager 106 can determine thatthe hand 112 is within a threshold distance (the gesture zone 118) ofthe electronic device 102, such as within three, five, seven, or nineinches of the electronic device 102. While the radar system 104 candetect objects within the radar field 110 at greater distances, thegesture zone 118 helps the electronic device 102 and the radar-gestureapplications to distinguish between intentional radar gestures by theuser and other kinds of motions that may resemble radar gestures.

The gesture zone 118 may be, in some cases, a fixed volume around theelectronic device that has a static size and/or shape that ispredefined, user-selectable, or determined via another method (e.g.,based on power requirements, remaining battery life, or another factor).In other cases, the gesture zone 118 may be a volume around theelectronic device that is dynamically and automatically adjustable bythe interaction manager 106, based on factors such as the velocity orlocation of the electronic device 102, a time of day, a state of anapplication running on the electronic device 102, or another factor. Thethreshold distance or gesture zone 118 can be determined based on anumber of relevant factors, such as battery level, location of theelectronic device, velocity of the electronic device, or data receivedfrom one or more of the radar system, other sensors, or applicationsrunning on the electronic device. The size and shape of the gesture zone118 may be symmetrical or asymmetrical and the extent of the gesture(e.g., the threshold distance from the electronic device) may bedifferent in different directions from the electronic device.

When the interaction manager 106 determines that the radar-gestureapplication is operating on the electronic device and that the hand 112(or other portion of the user) is within the gesture zone 118 of theelectronic device 102, the interaction manager 106 can, in response,cause the display 114 to present a feedback indicator 120. Similarly,when the interaction manager 106 determines that the hand 112 (or otherportion of the user) is outside the gesture zone 118 of the electronicdevice 102 and/or that the radar-gesture application is no longeroperating on the electronic device, the interaction manager 106 can, inresponse, cause the display 114 to stop presenting the feedbackindicator 120. The feedback indicator 120 is a user-perceivable element,such as a visual element that appears on an active area of the display114. The appearance of the feedback indicator 120 indicates that thehand 112 (or another portion of the user) is within the gesture zone 118and that the radar-gesture application has the capability to receiveradar-gesture input. The feedback indicator 120 can also be (or include)a light element that is not on the display (e.g., a light-emitting diode(LED) or an LED array mounted on a housing or bezel of the electronicdevice), a haptic element (e.g., a vibration element), and/or an audioelement (e.g., a user-perceivable sound).

In some implementations, before the determinations that theradar-gesture application is operating on the electronic device 102 andthat the hand 112 (or other portion of the user) is within the gesturezone 118, the electronic device can be in a state in which theelectronic device 102 or applications on the electronic device arecapable of receiving radar gestures, but the radar system 104 or theinteraction manager 106 prevents the electronic device or theapplication from receiving the gestures (e.g., because the user is notwithin the gesture zone). In these implementations, the determinationsthat the radar-gesture application is operating and that the hand 112 iswithin the gesture zone 118 cause the electronic device 102 to enter astate in which radar gestures are permitted (e.g., in which the radarsystem 104 or the interaction manager 106 permit the electronic deviceand/or the application to receive the radar gestures).

The feedback indicator 120 may be presented at or along an edge of thedisplay 114. In this document, the phrases “at an edge” and “along anedge” refer to being near or adjacent to an edge (e.g., adjacent to theedge with no gap or with a gap such as one pixel, two pixels, threepixels, and so forth). The feedback indicator 120 may have any of avariety of shapes, sizes, colors, and other visual parameters orproperties. Examples of the other visual parameters or propertiesinclude luminosity, color, contrast, shape, saturation, or opaqueness.Luminosity refers to the perceived brightness of an object by a human,and modifying the luminosity may include modifying luminance (e.g.,brightness), contrast, and/or opaqueness.

In some cases, the visual element may have an area that is a portion ofthe active area of the display 114 that has a luminosity or other visualproperty that is different from a luminosity or other visual property ofanother portion of the display 114 that is proximate to the visualelement. In this case, the visual element may also have a segment of anexterior border that is within a threshold distance from an edge of theactive area of the display (e.g., adjacent to the edge with no gap orwith a gap such as one pixel, two pixels, three pixels, one millimeter,two millimeters, three millimeters). While some of these examplesdescribe the feedback indicator 120 as presented at or along an edge ofthe display 114, the feedback indicator 120 may appear at a location onthe display 114 that is not an edge. For example, the edge of thedisplay 114 may include an area beginning at a border of the active areaof the display 114 and extending a distance from the border that is nomore than approximately 15 percent of a total length of the border ofthe display 114.

Consider an example illustrated in FIG. 1. A detail view 100-1 shows thehand 112 within the gesture zone 118. In the detail view 100-1, anexample of the feedback indicator 120 is presented on an example display114-1 with a higher level of luminosity, to indicate that theinteraction manager 106 has detected the hand 112 (e.g., the interactionmanager 106 has used one or more subsets of radar data to determine thatthe hand 112 is within the gesture zone 118) and that at least oneradar-gesture application is operating on the electronic device 102.Another detail view 100-2 shows the hand 112 outside the gesture zone118. In the detail view 100-2, a visual element 122 is presented on anexample display 114-2. The visual element 122 is shorter than, and has areduced luminosity (e.g., a 30 percent or 50 percent reduction of theluminosity) relative to, the feedback indicator 120 to indicate that theinteraction manager 106 has determined that the hand 112 is outside thegesture zone 118 (and/or that no radar-gesture application is operatingon the electronic device 102).

In the example shown in FIG. 1, the feedback indicator 120 and thevisual element 122 are both shown as a line located at a top edge of theelectronic device 102. In other implementations, the feedback indicator120 and/or the visual element 122 may be another size, another shape, orbe presented at another location. Further, the interaction manager 106may use one or more subsets of the radar data to enable the feedbackindicator 120 to track small motions of the hand 112 and to dynamicallyadjust a position of the feedback indicator 120 on the display 114. Thedynamic adjustments to the position of the feedback indicator 120 cancorrespond to movement of the user's hand 112 (or other portion of theuser) that is within the gesture zone 118. In addition to, or insteadof, adjustments of the position of the feedback indicator 120, theinteraction manager 106 can adjust other visual properties of thefeedback indicator 120 (e.g., luminosity, color, contrast, shape,saturation, and/or opaqueness) in a way that corresponds to the movementof the hand 112. This allows the user to see the feedback indicator 120move or otherwise provide dynamically responsive visual feedback thatcorresponds to the movement of the user's hand 112 (e.g., back andforth, up and down, and so forth).

In some implementations, the feedback indicator 120 may be presented asan adjustment to a visual element that is already being presented at oralong the edge of the active area of the display (e.g., a previouslypresented visual element indicating that the application operating onthe electronic device 102 has the capability to receive radar-gestureinput). For example, in the example shown in FIG. 1, the detail view100-2 shows a visual element 122 already being presented on the exampledisplay 114-2. When the user's hand 112 moves back into the gesture zone118, the visual element 122 may be adjusted to become the examplefeedback indicator 120, as shown in the detail view 100-1. In this case,the user may withdraw the hand 112 and, if the radar-gesture applicationis still running, the interaction manager 106 may stop presenting thefeedback indicator 120 and resume presenting the visual element 122.

A shown in FIG. 1, the adjustment to the previously presented visualelement 122 is an increase in a length and luminosity of the visualelement 122. In other cases, the adjustment may be a change in a size ofthe previously presented visual element 122. For example, the change insize may be an enlargement of an area of the previously presented visualelement 122. The enlargement may include extending the previouslypresented visual element 122 in a direction parallel to the edge of theactive area of the display, in a direction away from the edge of theactive area of the display, or both in the direction parallel to theedge of the active area of the display and in the direction away fromthe edge of the active area of the display. In other implementations,the adjustment may also or instead be a change in another visualproperty, such as a luminosity, a color, a contrast, a shape, asaturation, and/or an opaqueness.

In some implementations, the luminosity (or other visual parameter) ofthe feedback indicator 120 may vary as the feedback indicator 120extends across a distance from the edge of the active area of thedisplay 114 (e.g., have a luminosity at or along the edge of the display114 that decreases as the shape extends away from the edge, or viceversa). For example, the feedback indicator 120 may be presented as anarea of the display 114 that has a different luminosity than anotherarea of the display 114 (e.g., an area surrounding or near to thefeedback indicator 120) and that is adjacent to the edge of the display114. In another example, the feedback indicator 120 may be presented asa line, with a predetermined thickness, that has a different luminositythan the display 114 and that is adjacent to the edge of the display114.

The color of the feedback indicator 120 may be any suitable color thatcan be visually differentiated from the background of the display 114 onwhich it is presented. The color of the feedback indicator 120 maychange based on any of a variety of factors, such as an operationalstate of the electronic device 102 or an ambient background color of thedisplay 114. In some implementations, the interaction manager 106 candetermine a background color of a region of the display 114 on which thefeedback indicator 120 is, or will be, displayed. In response todetermining the background color, the interaction manager 106 can causethe display 114 to present the feedback indicator 120 in another colorthat is different from the background color. The different color of thefeedback indicator 120 can provide human-discernable contrast betweenthe feedback indicator 120 and the background color to make it easierfor the user to see the feedback indicator 120. In some cases, theinteraction manager 106 can continuously, automatically, and dynamicallyadjust the color of the feedback indicator 120, based on changes to thebackground color.

The feedback indicator 120, in some implementations, may appear, atleast in part, as a brief animation. For example, the feedback indicator120 may appear at the edge of the active display and then grow or shrinkbefore taking on a default appearance. Similarly, the color, luminosity,or shape may change as the feedback indicator 120 appears or disappears(e.g., if the radar-gesture application stops operating) before takingon the default appearance.

In some cases, the feedback indicator 120 may be an image that appearson the display 114, rather than an element that appears in a region ofthe display 114. The image may have visual parameters that are differentfrom the parameters of an ambient background of the display 114, such asluminosity, saturation, color, and so forth. In other cases, the ambientbackground may be an image, and the feedback indicator 120 is the sameimage, with different visual parameters, such as luminosity, saturation,color, and so forth. In this way, the feedback indicator 120 can improvethe user's experience by communicating to the user that the electronicdevice is operating in a mode in which radar gestures are available forinteracting with the electronic device 102. Additional details andexamples of the feedback indicator 120 are described with reference toFIG. 8.

In some implementations, the location of the feedback indicator 120 maybe determined based on an orientation of content on the display 114. Forexample, the interaction manager 106 may obtain the orientation of thecontent on the display 114 from the application manager 116 (or fromanother source). The interaction manager 106 can also determine, basedon the orientation of the content, a direction of the radar-gestureinput that can be used to interact with the content. Based on thedirection of the radar-gesture input, the interaction manager 106 cancause the display to present the feedback indicator 120 at a particularedge of the active area of the display 114 that corresponds to thedirection of the radar-gesture input. Thus, if the context of thedisplayed content is horizontal (e.g., the direction of the radargesture would be left-to-right or right-to-left), the feedback indicator120 is displayed at a top or bottom edge, to help indicate to the userthat the radar gestures are horizontal. Similarly, if the context of thedisplayed content is vertical (e.g., the direction of the radar gestureswould be bottom-to-top or top-to-bottom), the feedback indicator 120 isdisplayed at a side edge, to help indicate to the user that the radargestures are vertical.

Further, the interaction manager 106 may also be able to detect a changein an orientation of the electronic device 102 with respect to the user.For example, the user may rotate the device from a vertical to ahorizontal orientation to watch a video or from a horizontal to avertical orientation to read an article. Based on the change inorientation, the interaction manager 106 can cause the display 114 topresent the feedback indicator 120 on a different edge of the activedisplay. This different edge can maintain an orientation and location ofthe feedback indicator 120 with respect to the user (e.g., the feedbackindicator 120 moves or relocates as the orientation of the user to thedevice changes). Thus, if the feedback indicator 120 is positioned on atop edge of the display 114 and the user rotates the electronic device102, the location of the feedback indicator 120 changes from one edge toanother so that it remains on “top” with reference to the user. Asnoted, the interaction manager 106 also takes into account theorientation of the content, and these features can be used inconjunction with each other to present the feedback indicator 120 on thedisplay 114 at the location appropriate for the orientation of both thecontent on the display 114 and the orientation of the display 114 withrespect to the user.

In some implementations, the interaction manager 106 can determine thatthe radar-gesture application on the electronic device 102 is operatingin an immersive mode, such as a full-screen mode without any presentedcontrols. In response to this determination, the interaction manager cancause the display 114 to periodically present the feedback indicator120. For example, the display 114 can present the feedback indicator 120for a presentation time duration and then stop presenting the feedbackindicator 120 for a non-presentation time duration. Both thepresentation time duration and the non-presentation time duration may bepredetermined or selectable. In some cases, the time durations may beuser-selectable (e.g., by the user) or selected by the interactionmanager 106 based on various factors, such as the type of radar-gestureapplication running in the immersive mode (e.g., a game or a streamingmedia player), the status of the radar-gesture application, or thefrequency with which the user employs a radar gesture.

In some implementations, the feedback indicator 120 may fade ordisappear entirely when the user interacts with the electronic device102 using input other than a radar gesture (e.g., a touch or voiceinput). For example, while a radar-gesture application is operating onthe electronic device 102, the user may decide to start anotherapplication using a touch command. In this case, the feedback indicator120 may fade or disappear when the user picks up the electronic device102 or touches the display 114. When the user stops touching the display114 or puts down the electronic device 102, the feedback indicator 120reappears (or brightens) if one or more radar-gesture applications areoperating on the electronic device 102. The feedback indicator 120 mayreappear or brighten immediately when the touch or voice input ends, orafter a selectable time duration. Similarly, when the radar-gestureapplication is an application that provides an alert or notification,the feedback indicator 120 appears when the alert or notification isdisplayed, such as when a calendar reminder is displayed. When the userinteracts with the alert or notification using a radar gesture (e.g.,dismisses or resets the alert or notification), the feedback indicator120 disappears, unless other gesture-subscribed apps are running.

The feedback indicator 120 may be presented while the electronic device102 is in a locked state or an unlocked state. For example, theelectronic device 102 may present the feedback indicator 120 (toindicate that the hand 112 is within the gesture zone 118 and that theradar-gesture application is running) when a user is nearby (e.g.,within the recognition zone), but not authenticated, or when anauthenticated user is nearby. The locked and unlocked states refer to alevel of access to the electronic device 102. A locked state may be astate in which no user is authenticated and anyone using the device willhave less than full rights or access (e.g., no access or rights, orlimited access or rights). Examples of the locked state may include theaware and engaged modes of the electronic device 102 as describedherein. Similarly, an unlocked state can be a state in which at leastone user is authenticated, and that user has full rights and/or accessto the device. An example of the unlocked state is the active mode ofthe electronic device 102, as described herein. In some cases, thelocked or unlocked state may have varying characteristics, depending onthe type, configuration, or status (e.g., a battery level or aconnectivity status) of the electronic device 102. Accordingly,characteristics of the locked and unlocked states for different devicesor for the same device in different contexts may overlap, or includesimilar features, depending on those factors.

In more detail, consider FIG. 2, which illustrates an exampleimplementation 200 of the electronic device 102 (including the radarsystem 104, the interaction manager 106, the non-radar sensor 108, thedisplay 114, and the application manager 116) that can implement theinput methods for mobile devices. The electronic device 102 of FIG. 2 isillustrated with a variety of example devices, including a smartphone102-1, a tablet 102-2, a laptop 102-3, a desktop computer 102-4, acomputing watch 102-5, a gaming system 102-6, computing spectacles102-7, a home-automation and control system 102-8, a smart refrigerator102-9, and an automobile 102-10. The electronic device 102 can alsoinclude other devices, such as televisions, entertainment systems, audiosystems, drones, track pads, drawing pads, netbooks, e-readers, homesecurity systems, and other home appliances. Note that the electronicdevice 102 can be wearable, non-wearable but mobile, or relativelyimmobile (e.g., desktops and appliances).

In some implementations, exemplary overall lateral dimensions of theelectronic device 102 can be approximately eight centimeters byapproximately fifteen centimeters. Exemplary footprints of the radarsystem 104 can be even more limited, such as approximately fourmillimeters by six millimeters with antennas included. This requirementfor such a limited footprint for the radar system 104 is to accommodatethe many other desirable features of the electronic device 102 in such aspace-limited package (e.g., a fingerprint sensor, the non-radar sensor108, and so forth). Combined with power and processing limitations, thissize requirement can lead to compromises in the accuracy and efficacy ofradar gesture detection, at least some of which can be overcome in viewof the teachings herein.

The electronic device 102 also includes one or more computer processors202 and one or more computer-readable media 204, which includes memorymedia and storage media. Applications and/or an operating system (notshown) implemented as computer-readable instructions on thecomputer-readable media 204 can be executed by the computer processors202 to provide some or all of the functionalities described herein. Forexample, the processors 202 can be used to execute instructions on thecomputer-readable media 204 to implement the radar-based interactionmanager 106 and/or the application manager 116. The electronic device102 may also include a network interface 206. The electronic device 102can use the network interface 206 for communicating data over wired,wireless, or optical networks. By way of example and not limitation, thenetwork interface 206 may communicate data over a local-area-network(LAN), a wireless local-area-network (WLAN), a personal-area-network(PAN), a wide-area-network (WAN), an intranet, the Internet, apeer-to-peer network, point-to-point network, or a mesh network.

Various implementations of the radar system 104 can include aSystem-on-Chip (SoC), one or more Integrated Circuits (ICs), a processorwith embedded processor instructions or configured to access processorinstructions stored in memory, hardware with embedded firmware, aprinted circuit board with various hardware components, or anycombination thereof. The radar system 104 can operate as a monostaticradar by transmitting and receiving its own radar signals.

In some implementations, the radar system 104 may also cooperate withother radar systems 104 that are within an external environment toimplement a bistatic radar, a multistatic radar, or a network radar.Constraints or limitations of the electronic device 102, however, mayimpact a design of the radar system 104. The electronic device 102, forexample, may have limited power available to operate the radar, limitedcomputational capability, size constraints, layout restrictions, anexterior housing that attenuates or distorts radar signals, and soforth. The radar system 104 includes several features that enableadvanced radar functionality and high performance to be realized in thepresence of these constraints, as further described below with respectto FIG. 3. Note that in FIG. 2, the radar system 104 and the interactionmanager 106 are illustrated as part of the electronic device 102. Inother implementations, either or both of the radar system 104 and theinteraction manager 106 may be separate or remote from the electronicdevice 102.

These and other capabilities and configurations, as well as ways inwhich entities of FIG. 1 act and interact, are set forth in greaterdetail below. These entities may be further divided, combined, and soon. The environment 100 of FIG. 1 and the detailed illustrations of FIG.2 through FIG. 15 illustrate some of many possible environments anddevices capable of employing the described techniques. FIGS. 3-6describe additional details and features of the radar system 104. InFIGS. 3-6, the radar system 104 is described in the context of theelectronic device 102, but as noted above, the applicability of thefeatures and advantages of the described systems and techniques are notnecessarily so limited, and other implementations involving other typesof electronic devices may also be within the scope of the presentteachings.

FIG. 3 illustrates an example implementation 300 of the radar system 104that can be used to enable the input methods for mobile devices. In theexample 300, the radar system 104 includes at least one of each of thefollowing components: a communication interface 302, an antenna array304, a transceiver 306, a processor 308, and a system media 310 (e.g.,one or more computer-readable storage media). The processor 308 can beimplemented as a digital signal processor, a controller, an applicationprocessor, another processor (e.g., the computer processor 202 of theelectronic device 102) or some combination thereof. The system media310, which may be included within, or be separate from, thecomputer-readable media 204 of the electronic device 102, includes oneor more of the following modules: an attenuation mitigator 314, adigital beamformer 316, an angle estimator 318, or a power manager 320.These modules can compensate for, or mitigate the effects of,integrating the radar system 104 within the electronic device 102,thereby enabling the radar system 104 to recognize small or complexgestures, distinguish between different orientations of the user,continuously monitor an external environment, or realize a targetfalse-alarm rate. With these features, the radar system 104 can beimplemented within a variety of different devices, such as the devicesillustrated in FIG. 2.

Using the communication interface 302, the radar system 104 can provideradar data to the interaction manager 106. The communication interface302 may be a wireless or wired interface based on the radar system 104being implemented separate from, or integrated within, the electronicdevice 102. Depending on the application, the radar data may include rawor minimally processed data, in-phase and quadrature (I/Q) data,range-Doppler data, processed data including target location information(e.g., range, azimuth, elevation), clutter map data, and so forth.Generally, the radar data contains information that is usable by theinteraction manager 106 for the input methods for mobile devices.

The antenna array 304 includes at least one transmitting antenna element(not shown) and at least two receiving antenna elements (as shown inFIG. 4). In some cases, the antenna array 304 may include multipletransmitting antenna elements to implement a multiple-inputmultiple-output (MIMO) radar capable of transmitting multiple distinctwaveforms at a time (e.g., a different waveform per transmitting antennaelement). The use of multiple waveforms can increase a measurementaccuracy of the radar system 104. The receiving antenna elements can bepositioned in a one-dimensional shape (e.g., a line) or atwo-dimensional shape for implementations that include three or morereceiving antenna elements. The one-dimensional shape enables the radarsystem 104 to measure one angular dimension (e.g., an azimuth or anelevation) while the two-dimensional shape enables two angulardimensions to be measured (e.g., both azimuth and elevation). Exampletwo-dimensional arrangements of the receiving antenna elements arefurther described with respect to FIG. 4.

FIG. 4 illustrates example arrangements 400 of receiving antennaelements 402. If the antenna array 304 includes at least four receivingantenna elements 402, for example, the receiving antenna elements 402can be arranged in a rectangular arrangement 404-1 as depicted in themiddle of FIG. 4. Alternatively, a triangular arrangement 404-2 or anL-shape arrangement 404-3 may be used if the antenna array 304 includesat least three receiving antenna elements 402.

Due to a size or layout constraint of the electronic device 102, anelement spacing between the receiving antenna elements 402 or a quantityof the receiving antenna elements 402 may not be ideal for the angles atwhich the radar system 104 is to monitor. In particular, the elementspacing may cause angular ambiguities to be present that make itchallenging for conventional radars to estimate an angular position of atarget. Conventional radars may therefore limit a field of view (e.g.,angles that are to be monitored) to avoid an ambiguous zone, which hasthe angular ambiguities, and thereby reduce false detections. Forexample, conventional radars may limit the field of view to anglesbetween approximately −45 degrees to 45 degrees to avoid angularambiguities that occur using a wavelength of 5 millimeters (mm) and anelement spacing of 3.5 mm (e.g., the element spacing being 70% of thewavelength). Consequently, the conventional radar may be unable todetect targets that are beyond the 45-degree limits of the field ofview. In contrast, the radar system 104 includes the digital beamformer316 and the angle estimator 318, which resolve the angular ambiguitiesand enable the radar system 104 to monitor angles beyond the 45-degreelimit, such as angles between approximately −90 degrees to 90 degrees,or up to approximately −180 degrees and 180 degrees. These angularranges can be applied across one or more directions (e.g., azimuthand/or elevation). Accordingly, the radar system 104 can realize lowfalse-alarm rates for a variety of different antenna array designs,including element spacings that are less than, greater than, or equal tohalf a center wavelength of the radar signal.

Using the antenna array 304, the radar system 104 can form beams thatare steered or un-steered, wide or narrow, or shaped (e.g., as ahemisphere, cube, fan, cone, or cylinder). As an example, the one ormore transmitting antenna elements (not shown) may have an un-steeredomnidirectional radiation pattern or may be able to produce a wide beam,such as the wide transmit beam 406. Either of these techniques enablethe radar system 104 to illuminate a large volume of space. To achievetarget angular accuracies and angular resolutions, however, thereceiving antenna elements 402 and the digital beamformer 316 can beused to generate thousands of narrow and steered beams (e.g., 2000beams, 4000 beams, or 6000 beams), such as the narrow receive beam 408.In this way, the radar system 104 can efficiently monitor the externalenvironment and accurately determine arrival angles of reflectionswithin the external environment.

Returning to FIG. 3, the transceiver 306 includes circuitry and logicfor transmitting and receiving radar signals via the antenna array 304.Components of the transceiver 306 can include amplifiers, mixers,switches, analog-to-digital converters, filters, and so forth forconditioning the radar signals. The transceiver 306 can also includelogic to perform in-phase/quadrature (I/Q) operations, such asmodulation or demodulation. The transceiver 306 can be configured forcontinuous wave radar operations or pulsed radar operations. A varietyof modulations can be used to produce the radar signals, includinglinear frequency modulations, triangular frequency modulations, steppedfrequency modulations, or phase modulations.

The transceiver 306 can generate radar signals within a range offrequencies (e.g., a frequency spectrum), such as between 1 gigahertz(GHz) and 400 GHz, between 4 GHz and 100 GHz, or between 57 GHz and 63GHz. The frequency spectrum can be divided into multiple sub-spectrathat have a similar bandwidth or different bandwidths. The bandwidthscan be on the order of 500 megahertz (MHz), 1 GHz, 2 GHz, and so forth.As an example, different frequency sub-spectra may include frequenciesbetween approximately 57 GHz and 59 GHz, 59 GHz and 61 GHz, or 61 GHzand 63 GHz. Multiple frequency sub-spectra that have a same bandwidthand may be contiguous or non-contiguous may also be chosen forcoherence. The multiple frequency sub-spectra can be transmittedsimultaneously or separated in time using a single radar signal ormultiple radar signals. The contiguous frequency sub-spectra enable theradar signal to have a wider bandwidth while the non-contiguousfrequency sub-spectra can further emphasize amplitude and phasedifferences that enable the angle estimator 318 to resolve angularambiguities. The attenuation mitigator 314 or the angle estimator 318may cause the transceiver 306 to utilize one or more frequencysub-spectra to improve performance of the radar system 104, as furtherdescribed with respect to FIGS. 5 and 6.

A power manager 320 enables the radar system 104 to conserve powerinternally or externally within the electronic device 102. In someimplementations, the power manager 320 communicates with the interactionmanager 106 to conserve power within either or both of the radar system104 or the electronic device 102. Internally, for example, the powermanager 320 can cause the radar system 104 to collect data using apredefined power mode or a specific gesture-frame update rate. Thegesture-frame update rate represents how often the radar system 104actively monitors the external environment by transmitting and receivingone or more radar signals. Generally speaking, the power consumption isproportional to the gesture-frame update rate. As such, highergesture-frame update rates result in larger amounts of power beingconsumed by the radar system 104.

Each predefined power mode can be associated with a particular framingstructure, a particular transmit power level, or particular hardware(e.g., a low-power processor or a high-power processor). Adjusting oneor more of these affects the radar system's 104 power consumption.Reducing power consumption, however, affects performance, such as thegesture-frame update rate and response delay. In this case, the powermanager 320 dynamically switches between different power modes such thatgesture-frame update rate, response delay and power consumption aremanaged together based on the activity within the environment. Ingeneral, the power manager 320 determines when and how power can beconserved, and incrementally adjusts power consumption to enable theradar system 104 to operate within power limitations of the electronicdevice 102. In some cases, the power manager 320 may monitor an amountof available power remaining and adjust operations of the radar system104 accordingly. For example, if the remaining amount of power is low,the power manager 320 may continue operating in a lower-power modeinstead of switching to a higher-power mode.

The lower-power mode, for example, may use a lower gesture-frame updaterate on the order of a few hertz (e.g., approximately 1 Hz or less than5 Hz), and consume power on the order of a few milliwatts (mW) (e.g.,between approximately 2 mW and 4 mW). The higher-power mode, on theother hand, may use a higher gesture-frame update rate on the order oftens of hertz (Hz) (e.g., approximately 20 Hz or greater than 10 Hz),which causes the radar system 104 to consume power on the order ofseveral milliwatts (e.g., between approximately 6 mW and 20 mW). Whilethe lower-power mode can be used to monitor the external environment ordetect an approaching user, the power manager 320 may switch to thehigher-power mode if the radar system 104 determines the user isstarting to perform a gesture. Different triggers may cause the powermanager 320 to dynamically switch between the different power modes.Example triggers include motion or the lack of motion, appearance ordisappearance of the user, the user moving into or out of a designatedregion (e.g., a region defined by range, azimuth, or elevation), achange in velocity of a motion associated with the user, or a change inreflected signal strength (e.g., due to changes in radar cross section).In general, the triggers that indicate a lower probability of the userinteracting with the electronic device 102 or a preference to collectdata using a longer response delay may cause a lower-power mode to beactivated to conserve power.

Each power mode can be associated with a particular framing structure.The framing structure specifies a configuration, scheduling, and signalcharacteristics associated with the transmission and reception of theradar signals. In general, the framing structure is set up such that theappropriate radar data can be collected based on the externalenvironment. The framing structure can be customized to facilitatecollection of different types of radar data for different applications(e.g., proximity detection, feature recognition, or gesturerecognition). During inactive times throughout each level of the framingstructure, the power-manager 320 can turn off the components within thetransceiver 306 in FIG. 3 to conserve power. The framing structureenables power to be conserved through adjustable duty cycles within eachframe type. For example, a first duty cycle can be based on a quantityof active feature frames relative to a total quantity of feature frames.A second duty cycle can be based on a quantity of active radar framesrelative to a total quantity of radar frames. A third duty cycle can bebased on a duration of the radar signal relative to a duration of aradar frame.

Consider an example framing structure (not illustrated) for thelower-power mode that consumes approximately 2 mW of power and has agesture-frame update rate between approximately 1 Hz and 4 Hz. In thisexample, the framing structure includes a gesture frame with a durationbetween approximately 250 ms and 1 second. The gesture frame includesthirty-one pulse-mode feature frames. One of the thirty-one pulse-modefeature frames is in the active state. This results in the duty cyclebeing approximately equal to 3.2%. A duration of each pulse-mode featureframe is between approximately 8 ms and 32 ms. Each pulse-mode featureframe is composed of eight radar frames. Within the active pulse-modefeature frame, all eight radar frames are in the active state. Thisresults in the duty cycle being equal to 100%. A duration of each radarframe is between approximately 1 ms and 4 ms. An active time within eachof the active radar frames is between approximately 32 μs and 128 μs. Assuch, the resulting duty cycle is approximately 3.2%. This exampleframing structure has been found to yield good performance results.These good performance results are in terms of good gesture recognitionand presence detection while also yielding good power efficiency resultsin the application context of a handheld smartphone in a low-powerstate. Based on this example framing structure, the power manager 320can determine a time for which the radar system 104 is not activelycollecting radar data. Based on this inactive time period, the powermanager 320 can conserve power by adjusting an operational state of theradar system 104 and turning off one or more components of thetransceiver 306, as further described below.

The power manager 320 can also conserve power by turning off one or morecomponents within the transceiver 306 (e.g., a voltage-controlledoscillator, a multiplexer, an analog-to-digital converter, a phase lockloop, or a crystal oscillator) during inactive time periods. Theseinactive time periods occur if the radar system 104 is not activelytransmitting or receiving radar signals, which may be on the order ofmicroseconds (μs), milliseconds (ms), or seconds (s). Further, the powermanager 320 can modify transmission power of the radar signals byadjusting an amount of amplification provided by a signal amplifier.Additionally, the power manager 320 can control the use of differenthardware components within the radar system 104 to conserve power. Ifthe processor 308 comprises a lower-power processor and a higher-powerprocessor (e.g., processors with different amounts of memory andcomputational capability), for example, the power manager 320 can switchbetween utilizing the lower-power processor for low-level analysis(e.g., implementing the idle mode, detecting motion, determining alocation of a user, or monitoring the environment) and the higher-powerprocessor for situations in which high-fidelity or accurate radar datais requested by the interaction manager 106 (e.g., for implementing theaware mode, the engaged mode, or the active mode, gesture recognition oruser orientation).

Further, the power manager 320 can determine a context of theenvironment around the electronic device 102. From that context, thepower manager 320 can determine which power states are to be madeavailable and how they are configured. For example, if the electronicdevice 102 is in a user's pocket, then although the user is detected asbeing proximate to the electronic device 102, there is no need for theradar system 104 to operate in the higher-power mode with a highgesture-frame update rate. Accordingly, the power manager 320 can causethe radar system 104 to remain in the lower-power mode, even though theuser is detected as being proximate to the electronic device 102, andcause the display 114 to remain in an off or other lower-power state.The electronic device 102 can determine the context of its environmentusing any suitable non-radar sensor 108 (e.g., gyroscope, accelerometer,light sensor, proximity sensor, capacitance sensor, and so on) incombination with the radar system 104. The context may include time ofday, calendar day, lightness/darkness, number of users near the user,surrounding noise level, speed of movement of surrounding objects(including the user) relative to the electronic device 102, and soforth).

FIG. 5 illustrates additional details of an example implementation 500of the radar system 104 within the electronic device 102. In the example500, the antenna array 304 is positioned underneath an exterior housingof the electronic device 102, such as a glass cover or an external case.Depending on its material properties, the exterior housing may act as anattenuator 502, which attenuates or distorts radar signals that aretransmitted and received by the radar system 104. The attenuator 502 mayinclude different types of glass or plastics, some of which may be foundwithin display screens, exterior housings, or other components of theelectronic device 102 and have a dielectric constant (e.g., relativepermittivity) between approximately four and ten. Accordingly, theattenuator 502 is opaque or semi-transparent to a radar signal 506 andmay cause a portion of a transmitted or received radar signal 506 to bereflected (as shown by a reflected portion 504). For conventionalradars, the attenuator 502 may decrease an effective range that can bemonitored, prevent small targets from being detected, or reduce overallaccuracy.

Assuming a transmit power of the radar system 104 is limited, andre-designing the exterior housing is not desirable, one or moreattenuation-dependent properties of the radar signal 506 (e.g., afrequency sub-spectrum 508 or a steering angle 510) orattenuation-dependent characteristics of the attenuator 502 (e.g., adistance 512 between the attenuator 502 and the radar system 104 or athickness 514 of the attenuator 502) are adjusted to mitigate theeffects of the attenuator 502. Some of these characteristics can be setduring manufacturing or adjusted by the attenuation mitigator 314 duringoperation of the radar system 104. The attenuation mitigator 314, forexample, can cause the transceiver 306 to transmit the radar signal 506using the selected frequency sub-spectrum 508 or the steering angle 510,cause a platform to move the radar system 104 closer or farther from theattenuator 502 to change the distance 512, or prompt the user to applyanother attenuator to increase the thickness 514 of the attenuator 502.

Appropriate adjustments can be made by the attenuation mitigator 314based on pre-determined characteristics of the attenuator 502 (e.g.,characteristics stored in the computer-readable media 204 of theelectronic device 102 or within the system media 310) or by processingreturns of the radar signal 506 to measure one or more characteristicsof the attenuator 502. Even if some of the attenuation-dependentcharacteristics are fixed or constrained, the attenuation mitigator 314can take these limitations into account to balance each parameter andachieve a target radar performance. As a result, the attenuationmitigator 314 enables the radar system 104 to realize enhanced accuracyand larger effective ranges for detecting and tracking the user that islocated on an opposite side of the attenuator 502. These techniquesprovide alternatives to increasing transmit power, which increases powerconsumption of the radar system 104, or changing material properties ofthe attenuator 502, which can be difficult and expensive once a deviceis in production.

FIG. 6 illustrates an example scheme 600 implemented by the radar system104. Portions of the scheme 600 may be performed by the processor 308,the computer processors 202, or other hardware circuitry. The scheme 600can be customized to support different types of electronic devices andradar-based applications (e.g., the interaction manager 106), and alsoenables the radar system 104 to achieve target angular accuraciesdespite design constraints.

The transceiver 306 produces raw data 602 based on individual responsesof the receiving antenna elements 402 to a received radar signal. Thereceived radar signal may be associated with one or more frequencysub-spectra 604 that were selected by the angle estimator 318 tofacilitate angular ambiguity resolution. The frequency sub-spectra 604,for example, may be chosen to reduce a quantity of sidelobes or reducean amplitude of the sidelobes (e.g., reduce the amplitude by 0.5 dB, 1dB, or more). A quantity of frequency sub-spectra can be determinedbased on a target angular accuracy or computational limitations of theradar system 104.

The raw data 602 contains digital information (e.g., in-phase andquadrature data) for a period of time, different wavenumbers, andmultiple channels respectively associated with the receiving antennaelements 402. A Fast-Fourier Transform (FFT) 606 is performed on the rawdata 602 to generate pre-processed data 608. The pre-processed data 608includes digital information across the period of time, for differentranges (e.g., range bins), and for the multiple channels. A Dopplerfiltering process 610 is performed on the pre-processed data 608 togenerate range-Doppler data 612. The Doppler filtering process 610 maycomprise another FFT that generates amplitude and phase information formultiple range bins, multiple Doppler frequencies, and for the multiplechannels. The digital beamformer 316 produces beamforming data 614 basedon the range-Doppler data 612. The beamforming data 614 contains digitalinformation for a set of azimuths and/or elevations, which representsthe field of view for which different steering angles or beams areformed by the digital beamformer 316. Although not depicted, the digitalbeamformer 316 may alternatively generate the beamforming data 614 basedon the pre-processed data 608 and the Doppler filtering process 610 maygenerate the range-Doppler data 612 based on the beamforming data 614.To reduce a quantity of computations, the digital beamformer 316 mayprocess a portion of the range-Doppler data 612 or the pre-processeddata 608 based on a range, time, or Doppler frequency interval ofinterest.

The digital beamformer 316 can be implemented using a single-lookbeamformer 616, a multi-look interferometer 618, or a multi-lookbeamformer 620. In general, the single-look beamformer 616 can be usedfor deterministic objects (e.g., point-source targets having a singlephase center). For non-deterministic targets (e.g., targets havingmultiple phase centers), the multi-look interferometer 618 or themulti-look beamformer 620 are used to improve accuracies relative to thesingle-look beamformer 616. Humans are an example of a non-deterministictarget and have multiple phase centers 622 that can change based ondifferent aspect angles, as shown at 624-1 and 624-2. Variations in theconstructive or destructive interference generated by the multiple phasecenters 622 can make it challenging for conventional radars toaccurately determine angular positions. The multi-look interferometer618 or the multi-look beamformer 620, however, perform coherentaveraging to increase an accuracy of the beamforming data 614. Themulti-look interferometer 618 coherently averages two channels togenerate phase information that can be used to accurately determine theangular information. The multi-look beamformer 620, on the other hand,can coherently average two or more channels using linear or non-linearbeamformers, such as Fourier, Capon, multiple signal classification(MUSIC), or minimum variance distortion less response (MVDR). Theincreased accuracies provided via the multi-look beamformer 620 or themulti-look interferometer 618 enable the radar system 104 to recognizesmall gestures or distinguish between multiple portions of the user.

The angle estimator 318 analyzes the beamforming data 614 to estimateone or more angular positions. The angle estimator 318 may utilizesignal-processing techniques, pattern-matching techniques, ormachine-learning. The angle estimator 318 also resolves angularambiguities that may result from a design of the radar system 104 or thefield of view the radar system 104 monitors. An example angularambiguity is shown within an amplitude plot 626 (e.g., amplituderesponse).

The amplitude plot 626 depicts amplitude differences that can occur fordifferent angular positions of the target and for different steeringangles 510. A first amplitude response 628-1 (illustrated with a solidline) is shown for a target positioned at a first angular position630-1. Likewise, a second amplitude response 628-2 (illustrated with adotted line) is shown for the target positioned at a second angularposition 630-2. In this example, the differences are considered acrossangles between −180 degrees and 180 degrees.

As shown in the amplitude plot 626, an ambiguous zone exists for the twoangular positions 630-1 and 630-2. The first amplitude response 628-1has a highest peak at the first angular position 630-1 and a lesser peakat the second angular position 630-2. While the highest peak correspondsto the actual position of the target, the lesser peak causes the firstangular position 630-1 to be ambiguous because it is within somethreshold for which conventional radars may be unable to confidentlydetermine whether the target is at the first angular position 630-1 orthe second angular position 630-2. In contrast, the second amplituderesponse 628-2 has a lesser peak at the second angular position 630-2and a higher peak at the first angular position 630-1. In this case, thelesser peak corresponds to the target's location.

While conventional radars may be limited to using a highest peakamplitude to determine the angular positions, the angle estimator 318instead analyzes subtle differences in shapes of the amplitude responses628-1 and 628-2. Characteristics of the shapes can include, for example,roll-offs, peak or null widths, an angular location of the peaks ornulls, a height or depth of the peaks and nulls, shapes of sidelobes,symmetry within the amplitude response 628-1 or 628-2, or the lack ofsymmetry within the amplitude response 628-1 or 628-2. Similar shapecharacteristics can be analyzed in a phase response, which can provideadditional information for resolving the angular ambiguity. The angleestimator 318 therefore maps the unique angular signature or pattern toan angular position.

The angle estimator 318 can include a suite of algorithms or tools thatcan be selected according to the type of electronic device 102 (e.g.,computational capability or power constraints) or a target angularresolution for the interaction manager 106. In some implementations, theangle estimator 318 can include a neural network 632, a convolutionalneural network (CNN) 634, or a long short-term memory (LSTM) network636. The neural network 632 can have various depths or quantities ofhidden layers (e.g., three hidden layers, five hidden layers, or tenhidden layers) and can also include different quantities of connections(e.g., the neural network 632 can comprise a fully-connected neuralnetwork or a partially-connected neural network). In some cases, the CNN634 can be used to increase computational speed of the angle estimator318. The LSTM network 636 can be used to enable the angle estimator 318to track the target. Using machine-learning techniques, the angleestimator 318 employs non-linear functions to analyze the shape of theamplitude response 628-1 or 628-2 and generate angular probability data638, which indicates a likelihood that the user or a portion of the useris within an angular bin. The angle estimator 318 may provide theangular probability data 638 for a few angular bins, such as two angularbins to provide probabilities of a target being to the left or right ofthe electronic device 102, or for thousands of angular bins (e.g., toprovide the angular probability data 638 for a continuous angularmeasurement).

Based on the angular probability data 638, a tracker module 640 producesangular position data 642, which identifies an angular location of thetarget. The tracker module 640 may determine the angular location of thetarget based on the angular bin that has a highest probability in theangular probability data 638 or based on prediction information (e.g.,previously-measured angular position information). The tracker module640 may also keep track of one or more moving targets to enable theradar system 104 to confidently distinguish or identify the targets.Other data can also be used to determine the angular position, includingrange, Doppler, velocity, or acceleration. In some cases, the trackermodule 640 can include an alpha-beta tracker, a Kalman filter, amultiple hypothesis tracker (MHT), and so forth.

A quantizer module 644 obtains the angular position data 642 andquantizes the data to produce quantized angular position data 646. Thequantization can be performed based on a target angular resolution forthe interaction manager 106. In some situations, fewer quantizationlevels can be used such that the quantized angular position data 646indicates whether the target is to the right or to the left of theelectronic device 102 or identifies a 90-degree quadrant the target islocated within. This may be sufficient for some radar-basedapplications, such as user proximity detection. In other situations, alarger number of quantization levels can be used such that the quantizedangular position data 646 indicates an angular position of the targetwithin an accuracy of a fraction of a degree, one degree, five degrees,and so forth. This resolution can be used for higher-resolutionradar-based applications, such as gesture recognition, or inimplementations of the gesture zone, recognition zone, aware mode,engaged mode, or active mode as described herein. In someimplementations, the digital beamformer 316, the angle estimator 318,the tracker module 640, and the quantizer module 644 are togetherimplemented in a single machine-learning module.

These and other capabilities and configurations, as well as ways inwhich entities of FIG. 1-6 act and interact, are set forth below. Thedescribed entities may be further divided, combined, used along withother sensors or components, and so on. In this way, differentimplementations of the electronic device 102, with differentconfigurations of the radar system 104 and non-radar sensors, can beused to implement the input methods for mobile devices. The exampleoperating environment 100 of FIG. 1 and the detailed illustrations ofFIGS. 2-6 illustrate but some of many possible environments and devicescapable of employing the described techniques.

Example Methods

FIG. 7 depicts example method 700, which enables input methods formobile devices. The method 700 can be performed with an electronicdevice that includes, or is associated with, a display, an applicationthat is configured to receive input via radar gestures, and a radarsystem that can provide a radar field. The radar system and radar fieldcan provide radar data, based on reflections of the radar field fromobjects in the radar field, such as a user of the electronic device. Forexample, the radar data may be generated by, and/or received through,the radar system 104, as described with reference to FIG. 1. The radardata is used to determine interactions of the user with the electronicdevice, such as a presence of the user in the radar field, gestures madeby the user in the radar field, and movement of the user relative to theelectronic device. Based on the determination of the user's presence,movements, and gestures, the electronic device can enter and exitdifferent modes of functionality and present different visual elementson a display. The visual elements provide feedback to the user toindicate the user's posture with respect to the device, the availabilityof different functionalities for the electronic device, and the user'sinteractions with the electronic device. Additional examples of thevisual elements are described with respect to FIGS. 8-12.

The method 700 is shown as a set of blocks that specify operationsperformed but are not necessarily limited to the order or combinationsshown for performing the operations by the respective blocks. Further,any of one or more of the operations may be repeated, combined,reorganized, or linked to provide a wide array of additional and/oralternate methods. In portions of the following discussion, referencemay be made to the example operating environment 100 of FIG. 1 or toentities or processes as detailed in FIGS. 2-6, reference to which ismade for example only. The techniques are not limited to performance byone entity or multiple entities operating on one device.

At 702, based on radar data that is received through the radar system, aportion of a user is determined to be within a gesture zone of theelectronic device. For example, the interaction manager 106 or the radarsystem 104 can use the radar data from the radar system 104 to detectthat the user's hand 112 is within the gesture zone of the electronicdevice 102, as described with reference to FIG. 1 (e.g., within three,five, seven, or nine inches).

At 704, it is determined that an application operating on the electronicdevice has a capability to receive radar-gesture input. Theradar-gesture input (sometimes referred to as a radar gesture) isdefined by radar data that is generated by a radar system. For example,an application manager, such as the application manager 116 or theinteraction manager 106, can determine that an application operating onthe electronic device (e.g., the electronic device 102) has a capabilityto receive radar-gesture input (e.g., is a radar-gesture application).The radar data on which the radar-gesture input is based may begenerated by, and/or received through, the radar system 104, asdescribed with reference to FIG. 1.

At 706, responsive to the determination that the portion of the user iswithin the gesture zone of the electronic device and the determinationthat the application operating on the electronic device has thecapability to receive radar-gesture input, a feedback indicator isprovided on the display of the electronic device, the feedback indicatorindicating that the portion of the user is within the gesture zone andthe application can receive radar-gesture input. For example, inresponse to determining that the hand 112 is within the gesture zone 118and that the application operating on the electronic device 102 is aradar-gesture application, the interaction manager 106 can provide thefeedback indicator 120 on the display 114. Similarly, when the feedbackindicator is being provided, and the user's hand (or other portion ofthe user) is then determined to be outside the gesture zone (and/or thatthe radar-gesture application is no longer operating on the electronicdevice), the feedback indicator may cease being provided, even thoughanother visual element may still be provided. Thus, when a user who isoutside of the gesture zone reaches a hand toward the electronic deviceand into the gesture zone, the feedback indicator is displayed and whenthe user's hand is withdrawn, the feedback indicator is no longerdisplayed.

As described with reference to FIG. 1, the gesture zone is a region orvolume around the electronic device 102 within which the radar system104 (or another module or application) can detect the user's hand. Thegesture zone can be any suitable distance within which the radar systemcan recognize the user's hand, such as within three, five, seven, ornine inches. While the radar system 104 and interaction manager 106 maybe able to recognize a radar gesture and determine an action associatedwith the radar gesture from greater distances, the gesture zone helpsenable the electronic device to distinguish between intentional gesturesand other user movements that are not intended to be used to interactwith applications on the electronic device. Generally, the feedbackindicator is a user-perceivable element, such as a visual element thatappears on an active area of the display, that indicates that a part ofthe user, such as the user's hand 112, is close enough to the electronicdevice to use radar gestures to interact with the radar-gestureapplication (e.g., indicates that the user's hand is within the gesturezone). As noted with reference to FIG. 1, the gesture zone can havevarious sub-zones with different shapes and sizes within the gesturezone. The visual properties of the feedback indicator may vary in thedifferent sub-zones (e.g., the feedback indicator may get brighter orbigger as the user's hand gets closer).

The feedback indicator may be provided at or along an edge of thedisplay, as described with reference to FIG. 1, and may take any of avariety of shapes, sizes, colors, and other visual parameters orproperties (e.g., luminosity, color, contrast, shape, saturation, oropaqueness). In some implementations, as described with reference toFIG. 1, the visual element may have an area that is a portion of theactive area of the display that has a luminosity or other visualproperty that is different from a luminosity or other visual property ofanother portion of the display that is proximate to the visual element.In this case, the visual element may also have a segment of an exteriorborder that is within a threshold distance from an edge of the activearea of the display (e.g., adjacent to the edge with no gap or with agap such as one pixel, two pixels, three pixels, one millimeter, twomillimeters, three millimeters). Additionally, the luminosity (or othervisual parameter) of the feedback indicator may vary as the feedbackindicator extends across a distance from the edge of the active area ofthe display (e.g., have a luminosity at or along the edge of the displaythat decreases or increases as the shape extends away from the edge). Inother implementations, the feedback indicator may appear at a locationon the display that is not an edge (e.g., the feedback indicator may bepresented in an interior region of the display and not be adjacent to ortouch an edge of the display).

Additionally, the feedback indicator may be used to provide visualfeedback related to ongoing movements of the user's hand in the gesturezone. For example, as described with reference to FIG. 1, theinteraction manager 106 may use one or more subsets of the radar data toenable the feedback indicator to track the movements of the user's handand cause the feedback indicator to dynamically adjust a position of thefeedback indicator on the display in a manner that corresponds to themovements of the user's hand (or other portion of the user) within thegesture zone. In addition to or instead of adjustments of the positionof the feedback indicator, other visual properties of the feedbackindicator (e.g., luminosity, color, contrast, shape, saturation, and/oropaqueness) can be adjusted in a way that corresponds to the movement ofthe user's hand. These adjustments allow the feedback indicator toprovide dynamically responsive visual feedback that corresponds to themovement of the user's hand (e.g., back and forth, up and down, and soforth).

In some implementations of the method 700, the feedback indicator may bepresented as an adjustment to a visual element that is already beingpresented at or along the edge of the active area of the display (e.g.,a previously presented visual element indicating that the applicationoperating on the electronic device has the capability to receiveradar-gesture input). For example, in the example shown in FIG. 1, thedetail view 100-2 shows a visual element 122 already being presented onthe example display 114-2. When the user's hand 112 moves back into thegesture zone 118, the visual element 122 may be adjusted to become theexample feedback indicator 120, as shown in the detail view 100-1. Inthis case, the user may withdraw the hand 112 and, if the radar-gestureapplication is still running, the interaction manager 106 may stoppresenting the feedback indicator 120 and resume presenting the visualelement 122.

As noted with reference to FIG. 1, the adjustment to the previouslypresented visual element is an increase in a length and luminosity ofthe visual element. In other cases, the adjustment may be a change in asize of the previously presented visual element. For example, the changein size may be an enlargement of an area of the previously presentedvisual element. The enlargement may include extending the previouslypresented visual element an increased distance in a direction parallelto the edge of the active area of the display, an increased distance ina direction away from the edge of the active area of the display, orboth in the direction parallel to the edge of the active area of thedisplay and in the direction away from the edge of the active area ofthe display. In other implementations, the adjustment may also orinstead be a change in another visual property, such as a luminosity, acolor, a contrast, a shape, a saturation, and/or an opaqueness.

The color of the feedback indicator may be any suitable color that canbe visually differentiated from the background of the display on whichit is presented. The color may change based on any of a variety offactors, as described with reference to FIG. 1. In some implementationsof the method 700, a component of the electronic device (e.g., theinteraction manager 106), can determine a background color of a regionof the display on which the feedback indicator is displayed. In responseto determining the background color, the feedback indicator may bepresented in another color that is different from the background color,which provides human-discernable contrast between the feedback indicatorand the background color, as described with reference to FIG. 1. In somecases, the color of the feedback indicator can be continuously,automatically, and dynamically adjusted, based on changes to thebackground color.

The feedback indicator may appear, at least in part, as a briefanimation. For example, the feedback indicator may appear at the edge ofthe active display and then grow or shrink before taking on a defaultappearance. Similarly, the color, luminosity, or shape may change as thefeedback indicator appears or disappears (e.g., if the radar-gestureapplication stops operating) before taking on the default appearance.Further, the feedback indicator may be an image that appears on thedisplay, rather than an element that appears in a region of the display.The image may have visual parameters that are different from theparameters of an ambient background of the display, such as luminosity,saturation, or color. In other cases, the ambient background may be animage, and the feedback indicator is the same image, with differentvisual parameters, such as luminosity, saturation, color, and so forth.In this way, the feedback indicator can improve the user's experience bycommunicating to the user that a radar-gesture application is operatingon the electronic device.

In some implementations of the method 700, the location of the feedbackindicator may be determined based on an orientation of content on thedisplay and/or a direction of the radar-gesture input that is used tointeract with the content. For example, a component of the electronicdevice, such as the interaction manager 106, may obtain the orientationof the content on the display (e.g., from the application manager 116).Based on the orientation of the content, the display can determine thedirection of the radar-gesture input that can be used to interact withthe content and provide the feedback indicator at a particular edge ofthe active area of the display that corresponds to the direction of theradar input. Thus, as described with reference to FIG. 1, if the contextof the displayed content is horizontal, the feedback indicator isdisplayed at a top edge and, if the context of the displayed content isvertical, the feedback indicator is displayed at a side edge.

Further, a change in an orientation of the electronic device withrespect to the user may be detected and, based on the change inorientation, the feedback indicator may be provided on a different edgeof the display, in order to maintain the orientation and location of thefeedback indicator with respect to the user. For example, as describedwith reference to FIG. 1, the user may rotate the device from a verticalto a horizontal orientation to watch a video or from a horizontal to avertical orientation to read an article. Based on the change inorientation, the interaction manager 106 can cause the display 114 toprovide the feedback indicator 120 on a different edge of the activedisplay, in order to maintain an orientation and location of thefeedback indicator 120 with respect to the user. As noted, theorientation of the content may also be accounted for, and these featurescan be used in conjunction with each other to provide the feedbackindicator on the display at the location appropriate for the orientationof both the content on the display and the orientation of the displaywith respect to the user.

In some cases, it can be determined that the radar-gesture applicationrunning on the electronic device is operating in an immersive mode(e.g., in a full-screen mode without any presented controls). Inresponse to this determination, the display can periodically provide thefeedback indicator. For example, as described with reference to FIG. 1,the feedback indicator can be provided on the display for a presentationtime duration and then stop being provided for a non-presentation timeduration. Both the presentation time duration and the non-presentationtime duration may be predetermined or selectable. The time durations maybe selectable (e.g., by the user or by the interaction manager 106 basedon various factors, such as the type of radar-gesture applicationrunning in the immersive mode, the status of the radar-gestureapplication, or the frequency with which the user employs a radargesture).

The feedback indicator may fade or disappear entirely when the userinteracts with the electronic device using input other than a radargesture (e.g., a touch or voice input). For example, as described withreference to FIG. 1, the user may decide to start an application using atouch command on the electronic device, while a radar-gestureapplication is also running. In this case, the feedback indicator mayfade or disappear when the user picks up the electronic device ortouches the display. The feedback indicator restarts when the user stopstouching the display or puts down the electronic device (if one or moreradar-gesture applications are still operating). The feedback indicatormay reappear or brighten immediately when the touch or voice input ends,or after a selectable default time duration. Similarly, when theradar-gesture application is an application that provides an alert ornotification, the feedback indicator appears when an alert ornotification is displayed and, when the user interacts with the alert ornotification using a radar gesture, the feedback indicator disappears,unless other gesture-subscribed apps are running.

The feedback indicator can be provided while the electronic device 102is in a locked state or an unlocked state. Thus, the electronic devicemay provide the feedback indicator when a part of the user is within thegesture zone (and a radar-gesture application is running), whether theuser is authenticated or not authenticated. As described with referenceto FIG. 1, the locked and unlocked states refer to a level of access tothe electronic device. A locked state may be a state in which no user isauthenticated and anyone using the device will have less than fullrights or access (e.g., no access or rights, or limited access orrights). Examples of the locked state may include the aware and engagedmodes of the electronic device as described herein. Similarly, anunlocked state can be a state in which at least one user isauthenticated, and that user has full rights and/or access to thedevice. An example of the unlocked state is the active mode of theelectronic device, as described herein.

These techniques for the input methods for mobile devices may be moresecure than other authentication and feedback techniques. For example, auser's position, orientation, or use of radar gestures (especiallyuser-defined gestures, micro-gestures, and posture or position-basedgestures) are typically not duplicable or obtainable by an unauthorizedperson (unlike, for example, a password). Further, a radar image of theuser (e.g., based on the radar data described above), even if itincludes the user's face, does not visually identify the user like aphotograph or video may do. Even so, further to the descriptions above,the user may be provided with controls allowing the user to make anelection as to both whether and when any of the systems, programs,managers, modules, or features described in this document may enablecollection of user information (e.g., images of the user, radar datadescribing the user, information about a user's social network, socialactions or activities, profession, a user's preferences, or a user'scurrent location), and whether and when the user is sent content orcommunications from a server. In addition, certain data may be treatedin one or more ways before it is stored or used, so that personallyidentifiable information is removed. For example, a user's identity maybe treated so that no personally identifiable information can bedetermined for the user, or a user's geographic location may begeneralized where location information is obtained (such as to a city,zip/postal code, or state level), so that a particular location of auser cannot be determined. Thus, the user may have control over whatinformation is collected about the user, how that information is used,and what information is provided to or about the user.

Example Visual Elements

As noted, the techniques and systems described herein can enable theelectronic device 102 to provide feedback and notification to make theuser aware of an available radar-gesture input mode and, in some cases,provide additional feedback regarding the use and results of the radargestures. The feedback and notification are provided by one or moreuser-perceivable elements, such as visual elements that are presented onthe display 114. The techniques and systems can also enable adetermination of the user's absence, presence, and location, which canbe used to provide a more-responsive and more-efficient authenticationprocess. For example, the techniques enable the electronic device toanticipate when the user is ready to be authenticated and tomore-accurately determine when to lock the device when the user is away.The feedback, visual elements, and other features enable interactionsthat are more convenient and less frustrating because the user is awareof the input modes and can be confident about different ways in whichthe device can interact and receive input. FIGS. 8-15 illustrateexamples of the electronic device 102 running a radar-gestureapplication and describe examples of the visual elements that can bepresented on the display to provide feedback to the user. Examples ofthe electronic device operating in multiple different modes and examplesof the visual elements that can be presented on the display in thedifferent modes are also described.

Consider FIG. 8, which illustrates generally, at 800, an example of avisual feedback element that can be used to indicate that aradar-gesture application is running on the electronic device 102. InFIG. 8, a detail view 800-1 shows an example display 114-3 to indicate astate of the electronic device 102 with no radar-gesture applicationrunning Another state of the electronic device 102, in which at leastone radar-gesture application is running, is shown on another exampledisplay 114-4. A visual element 802 at the top of the example display114-4 indicates that the electronic device 102 can receive input throughradar gestures, as described above. The visual element 802 is shown asan illuminated line, but, as noted above, may be presented at anotherlocation, at a different illumination level (e.g., only partiallyilluminated), or as another shape or type of element. For example, inanother detail view 800-2, an example display 114-5 is shown to indicatethe state of the electronic device 102 with no radar-gesture applicationrunning Another state of the electronic device 102, in which at leastone radar-gesture application is running, is shown on another exampledisplay 114-6. A visual element 804 at the top of the example display114-6 indicates that the electronic device 102 can receive input throughradar gestures, as described above. The visual element 804 is shown asan illuminated area (e.g., a glowing area). As with the visual element802, the visual element 804 could be presented at another location onthe display 114-6, at a different illumination level (e.g.,more-illuminated or less-illuminated), or as another shape or type ofelement. Note that for clarity, no other elements (e.g., time, date, orapplication launch icons) are shown on the example displays 114-3through 114-6. In other implementations, however, the visual elements802 or 804 may be displayed along with other content on the display.Further, the visual elements 802 or 804 may be displayed while theelectronic device 102 is in the aware mode, the engaged mode, the activemode, or another mode.

In some implementations, the electronic device 102 can also providemore-detailed visual feedback that is related to the availability ofradar gestures. For example, the interaction manager 106 may cause thedisplay 114 to present other visual elements that provide feedbackregarding input received through radar-based radar gestures. FIGS. 9-12illustrate additional details of some of the ways that visual elementscan be used to provide the feedback related to the use of radargestures.

For instance, consider FIGS. 9A-9D, which illustrate generally, at 900,examples of the feedback indicator 120 that may be used to indicate thata user's hand is within a gesture zone that enables a radar-gestureapplication to receive radar-gesture input (e.g., the gesture zone 118).The gesture zone 118 is an area around the electronic device 102 (or theradar system 104) within which the electronic device 102 can receive,interpret, and act on radar gestures, such as a swipe or a pinch. Thegesture zone can extend any suitable distance from the electronic device102 (e.g., approximately three, approximately five, approximately seven,or approximately nine inches).

In FIG. 9A, an example display 114-7 is shown in a state in which atleast one radar-gesture application is running (e.g., similar to theexample display 114-6 described with reference to FIG. 8). A user's hand902 is shown near the example display 114-7, but outside the gesturezone 118 (the border of the gesture zone is shown as a dotted line 904).An example feedback indicator 906 (visual element 906) is shown as aglowing area (e.g., an area or shape with varying brightness, color, orother properties) near the top of the example display 114-7 with aluminosity that changes with distance from the top. In otherimplementations, the visual element 906 could be presented at anotherlocation or as another shape or type of element (e.g., a line, as shownin the detail view 800-1 of FIG. 8). In FIG. 9B, the user's hand 902moves toward the electronic device and crosses the border 904 of thegesture zone, as shown by the arrow 908. In response to the electronicdevice detecting the movement 908, another visual element 910 replacesthe visual element 906, as shown on an example display 114-8. In thisexample, the visual element 910 is a glowing area that is larger thanthe visual element 906 and has a different brightness or luminosity(e.g., less-, more-, or fully-illuminated). In other implementations,the visual element 910 could also be presented at another location or asanother shape or type of element.

As shown in FIG. 9C (and described with reference to FIG. 1), when theuser's hand 902 is within the border 904 of the gesture zone, the visualelement 910 can be used to provide feedback that indicates smaller,non-gesture motion of the user's hand 902, which are represented by adouble-ended arrow 912. For example, as shown on an example display114-9, the visual element can move to indicate the user's hand movementsby moving back and forth with the user's hand, as shown by an arrow 914.In FIG. 9D, the user's hand 902 is withdrawn outside the border 904 ofthe gesture zone, as shown by an arrow 916. In response to the motion ofthe user's hand, the display 114 returns to the state as shown in theexample display 114-7, in which the visual element 906 is displayed nearthe top edge of the display 114.

In some implementations (not shown in FIG. 9A-9D), the non-gesturemotions can be represented by other visual elements or changes to thevisual elements. For example, a size and/or shape can change, or acenter or focal point of the shape can move to represent the motions(while the shape itself remains stationary). Additionally oralternatively, changes to an intensity of the brightness or color can beused to represent the motion (e.g., the brightness or color of theshape, or part of the shape, change in accordance with the non-gesturemotions. The visual elements 906 and 910, along with the motion of thevisual element 910, can help the user understand when gestures areavailable, and provide feedback that indicates the electronic device 102is aware of the relative position of the user's hand, which can improvethe user's experience with the electronic device 102. The embodimentsshown in FIG. 9A-9D are examples 12-18 in which visual properties of thefeedback indicator are dynamically adjusted corresponding to thedistance to the electronic device and/or the movement of the portion ofthe user in the gesture zone.

As described with reference to FIG. 9C, the electronic device 102 canprovide visual feedback to represent smaller, non-gesture motion of theuser's hand in the gesture zone, such as moving a visual element backand forth on the display, corresponding to the motion of the user'shand. Similarly, when the user makes a radar gesture (e.g., a swipinggesture to skip a song or an omni-gesture to dismiss an alert ornotification), the electronic device 102 can provide feedback to notifythe user that the gesture has been successfully received or that agesture attempt was received but it was not clear enough to be confirmedas a radar gesture. For example, FIG. 10 illustrates generally, at 1000,a sequence of example visual elements that can be used to notify theuser that a gesture has been successfully received.

In FIG. 10, an example display 114-10 is shown in a state in which atleast one radar-gesture application is running and a user's hand 1002 iswithin a boundary of a gesture zone (e.g., similar to the staterepresented by the example display 114-8 described with reference toFIG. 9B). The example display 114-10 is presenting a visual element1004, shown as an illuminated line near the top of the example display114-10, to indicate the availability of radar gestures and that theuser's hand 1002 is within the gesture zone. In the example of FIG. 10,the user makes a sliding or swiping gesture from left to right, as shownby the arrow 1006. In response to the motion 1006 of the user's hand1002, the visual element 1004 also moves, as shown in a sequence 1008(shown within a dashed-line rectangle). An example display 114-11illustrates the beginning of the sequence 1008, as the visual element1004 begins moving to the right, as shown by an arrow 1010.

The sequence 1008 continues in another example display 114-12, in whichthe visual element 1004 bends around a corner of the example display114-12, as shown by an arrow 1012. The visual element 1004 can continuedown a side of the display 114 for a variable distance (e.g., as soon asa trailing end of the visual element completes the bend or after thetrailing end has traveled a particular distance along the side) and thendisappear. Continuing the sequence 1008 in another example display114-13, the visual element 1004 reappears or regenerates from the leftside of the example display 114-13 and moves toward the center position,as shown by an arrow 1014. In some implementations, the visual element1004 can reappear or regenerate at the initial position (as shown in theexample display 114-10), rather than from the left side. When thesequence 1008 is complete, the display returns to the state as shown inthe example display 114-10, with the visual element 1004 displayed nearthe top of the display 114 and may subtly track the user's hand 1002while the hand remains within the boundary of the gesture zone. Themotion of the visual element 1004 can help the user understand whenradar gestures have been accepted and when the gesture is complete,which can improve the user's experience with the electronic device 102.

Consider an example in which a user is listening to music with aradar-gesture application on a smartphone (e.g., the electronic device102). The user decides to skip a track and makes a radar gesture overthe smartphone. The radar gesture may be a swipe in either direction(e.g., left-to-right to skip to the next track or right-to-left torestart the current track or skip to a previous track). When the user'shand enters the gesture zone, a visual element, such as the feedbackindicator 120, is presented. As the user begins the radar gesture, thesmartphone (e.g., through the interaction manager 106) presents thevisual element in the sequence 1008, as described with reference to FIG.10. In this way, the visual element can provide the user with feedbackabout the success of the radar gesture.

Note that the sequence 1008 begins when the user begins the gesture, butthe gesture and the sequence 1008 may be completed at different times.Further, as described above, while the visual element 1004 is shown asan illuminated line near the top of the display 114, the visual element1004 could be presented at another location or as another shape or typeof element (e.g., as shown in FIGS. 9A-9D or in the detail view 800-2 ofFIG. 8). The sequence 1008 could also begin at another location on thedisplay 114 and proceed in another direction, such as right to left, topto bottom, or bottom to top (e.g., if a radar gesture moved from rightto left, top to bottom, or bottom to top). Another example of a sequencethat shows a successful radar gesture (not shown in FIG. 10) includes avisual element that expands and brightens, then collapses on itself andbriefly disappears, and then regenerates (e.g., from its originalposition). Other examples also include a visual element that bends orflexes (e.g., at one end, both ends, in the middle, or at anotherlocation) to show a successful radar gesture, such as a gesture made ina direction perpendicular to the display 114 or a gesture with acomponent that is perpendicular to the display 114. In other cases, thevisual element 1004 may disappear at or before it reaches the corner, orit may continue down a side of the display 114 around the corner, oreven move all the way around the display 114.

In some cases, as described herein, the visual element may be hiddeneven when radar gestures are available (e.g., because the userinteracted with a voice or touch input, or in order to reduce the riskof screen burn-in). In this situation, the visual element, such as thevisual element 1004, may still be shown when the user makes a successfulradar gesture. Consider a variation of the music player example above,in which the visual element is hidden while the user is listening tomusic and using a voice input to open another application. In thisexample, the user performs a radar gesture to skip a song, and thedisplay presents the sequence 1008 to notify the user that the radargesture was successful.

FIG. 11 illustrates generally, at 1100, a sequence of example visualelements that can be used to notify the user that a gesture has failedto be successfully made or received. In FIG. 11, an example display114-14 is shown in a state in which at least one radar-gestureapplication is running and in which a user's hand 1102 is within theboundary of a gesture zone (e.g., similar to the state represented inthe example display 114-8 described with reference to FIG. 9B). Theexample display 114-14 is presenting a visual element 1104, shown as anilluminated line near the top of the example display 114-14, to indicatethe availability of radar gestures and that the user's hand 1102 iswithin the gesture zone. In the example of FIG. 11, assume that the userattempts to make a sliding or swiping gesture from left to right, butfails to meet sufficient standards for a swiping gesture or did notcorrespond to a radar gesture for a radar-gesture application on theelectronic device. For example, as shown by a curved arrow 1106, theuser's hand 1102 may fail to travel sufficient distance in a relevantdirection before withdrawing. In this case, when the electronic device102 (or the radar system 104) detects the motion 1106 of the user's hand1102, which lacks sufficient definition to be successfully determined tobe a radar gesture, the visual element 1104 moves as shown in a sequence1108 (shown within a dashed-line rectangle). An example display 114-15illustrates the beginning of the sequence 1108, as the visual element1104 begins moving to the right, as shown by an arrow 1110.

Continuing the sequence 1108 in another example display 114-16, thevisual element 1104 has stopped before reaching an opposite edge of theexample display 114-16 and has shrunk (compared to its starting lengthas shown in the example display 114-14). The sequence 1108 continues inanother example display 114-17, in which the visual element 1104reverses direction and begins to move back toward its original location(the center in this example), as shown by another arrow 1112. The visualelement 1104 also begins to grow back to its original length. In otherimplementations, rather than stopping and shrinking, the visual element1104 may slow and bounce before reversing direction. When the sequence1108 is complete, the display returns to the state as shown in theexample display 114-14, with the visual element 1104 displayed near thetop of the example display 114 and subtly tracking the user's hand 1102while it remains within the boundary of the gesture zone (e.g., as shownin FIG. 9A-9D). The motion of the visual element 1104 can help the userunderstand when a gesture has not been successfully completed so thatthe user can learn techniques for making successful radar gestures andbecome aware when an attempted gesture fails (e.g., so it can beattempted again, if necessary), which can improve the user's experiencewith the electronic device 102.

Note that the sequence 1108 may begin when the electronic device 102 (orthe interaction manager 106) detects (e.g., using one or more subsets ofthe radar data) that the user has attempted a radar gesture, but alsodetermines that the gesture fails to meet at least one criterion that isnecessary for acceptance. Accordingly, the attempted gesture and thesequence 1108 may be completed at different times, depending on thenature of the attempted gesture and the speed of the sequence 1108.Further, as described above, while the visual element 1104 is shown as apartially illuminated line near the top of the display 114, the visualelement 1104 may be presented at another location or as another shape ortype of element (e.g., as shown in FIGS. 9A-9D or in the detail view800-2 of FIG. 8). The sequence 1108 could also begin at another locationon the display 114 and proceed in another direction, such as right toleft, top to bottom, or bottom to top (e.g., if an attempted radargesture moved from right to left, top to bottom, or bottom to top).Other examples of sequences that show an unsuccessful radar gestureattempt include a visual element that partially collapses on itself,such as by briefly shrinking, and then returns to its original size andposition.

In some implementations, the electronic device 102 includes agesture-paused mode that can turn off or suspend the radar gesturecapabilities of the electronic device 102 when conditions indicate thatthe system may be inefficient or ineffective at receiving orinterpreting the gestures. For example, when the electronic device 102is moving at a velocity above a threshold, or when the direction inwhich the electronic device 102 is moving changes rapidly andrepeatedly, the electronic device can enter the gesture-paused mode andprovide visual feedback to the user. The electronic device 102 maydetermine to enter the gesture-paused mode based on input from any of avariety of sensors, including a radar sensor (e.g., the radar system104), an inertial measurement unit (IMU), a proximity sensor (e.g., anactive infrared proximity sensor), and so forth. For example, if theuser is walking and listening to audio content with the electronicdevice 102 in the user's hand, swinging back and forth, the motion maybe similar to a radar-based swipe gesture, but the user does not intendto skip tracks or adjust the volume. Accordingly, because the motion ofthe electronic device 102 can introduce ambiguity into the gestureinterpretation process, the electronic device 102 may determine to enterthe gesture-paused mode until the ambiguity is resolved (e.g., the userstops walking).

Consider FIG. 12, which illustrates generally, at 1200, example visualelements that may be used to indicate that a radar-gesture applicationis available to receive radar-gesture input, but that gestures arecurrently paused. The gesture-paused mode may be activated wheneverradar gestures are available, whether the user's hand is in or out ofthe gesture zone. In FIG. 12, an example display 114-18 is shown in astate in which at least one radar-gesture application is running and auser's hand is within the boundary of a gesture zone (e.g., similar tothe state represented in the example display 114-8 described withreference to FIG. 9B). The example display 114-18 is presenting a visualelement 1202, shown as an illuminated line near the top of the exampledisplay 114-18, to indicate the availability of radar gestures and thatthe user's hand 1102 is within the gesture zone. If the user takes anaction that causes the electronic device 102 to enter the gesture-pausedmode (e.g., the user's hand begins moving back and forth as the user iswalking, as shown by an arrow 1204), the visual element 1202 can change,as shown in a sequence 1206 (within a dashed-line rectangle).

An example display 114-19 illustrates the beginning of the sequence 1206as another visual element 1208 replaces the visual element 1202, inresponse to the electronic device 102 detecting the movement 1204. Asshown on an example display 114-19, the visual element 1208 is anotherline that is shorter and dimmer than the visual element 1202. Inimplementations in which the visual element 1202 has a particular color,the visual element 1208 may have a different color from that of thevisual element 1202 (e.g., the color may change from the particularcolor to another color, such as grey or white). The sequence 1206continues in another example display 114-20, in which the visual element1208 begins moving to the right, as shown by an arrow 1210. Continuingthe sequence 1206 in another example display 114-21, the visual element1208 moves to the left as shown by an arrow 1212. In the sequence 1206,the visual element 1208 may stop and reverse direction before it reachesa side of the display or go all the way to the edge before reversingdirection. In some implementations, the visual element 1208 may furthershrink when it stops to reverse directions and then return to anothersize when, after, or as, it begins moving in the opposite direction.Further, the oscillation of the visual element 1208 may match thecondition upon which the gesture-paused mode is based. For example, inthe case of the user's arms swinging, the velocity or frequency of theoscillation of the visual element 1208 may approximately match thevelocity or frequency of the user's hand moving.

As described above, while the visual element 1208 is shown as anilluminated line near the top of the display 114, the visual element1208 can be presented at another location or as another shape or type ofelement (e.g., as shown in FIGS. 9A-9D or in the detail view 800-2 ofFIG. 8). The sequence 1108 can also begin at another location on thedisplay 114 and proceed in another direction, such as right to left, topto bottom, or bottom to top (e.g., depending on the orientation ofcontent on the display 114, the direction of the radar-gesture input, oranother factor).

When the electronic device 102 exits the gesture-paused mode, thesequence 1206 is complete and the display 114 returns to an appropriatestate, depending on whether there are radar-gesture applications runningand on the location of the user's hand. The sequence 1206 of motion ofthe visual element 1208 can help the user understand when gestures maybe paused and allow the user to adjust how the electronic device 102 isused to avoid or take advantage of the gesture-paused mode, which canimprove the user's experience with the electronic device 102.

In some cases (not shown in FIG. 12), the user's motion may notintroduce ambiguity, such as a situation in which the user walking withthe electronic device and holding it steady in front of the user. Inthese cases, the electronic device does not enter the gesture-pausedmode and the visual element 1202 may change one or more visualparameters to alert the user that radar gestures are available, evenwhile the user and the electronic device are in motion. For example, thevisual element 1202 may change from a default color to another color(e.g., from grey to blue, grey to white, or white to blue).

In some implementations, the electronic device 102 can determine thatthe radar-gesture application running on the electronic device 102 isoperating in an immersive mode (e.g., in a full-screen mode without anypresented controls). In response to this determination, the display canperiodically provide the visual elements described with reference toFIGS. 8-12 (e.g., the visual elements 802, 804, 906, 910, 1004, 1104,1202, and/or 1208). For example, the visual element can be provided onthe display for a time duration and then stop being provided for anothertime duration. The time durations may be selectable (e.g., by a user orby the electronic device 102, based on factors such as the type ofradar-gesture application running in the immersive mode, the status ofthe radar-gesture application, or the frequency with which the useremploys a radar gesture).

Note that the visual elements described above with reference to FIGS.8-12 (e.g., the visual elements 802, 804, 906, 910, 1004, 1104, 1202,1208, and/or the feedback indicator 120), may be presented in anysuitable color that can be visually differentiated from the backgroundof the display on which it is presented. Further, the color of thevisual elements may change based on any of a variety of factors, such asan operational state of the electronic device or an ambient backgroundcolor of the display. For example, the interaction manager 106 (oranother entity, module, or manager) can determine a background color ofa region of the display on which the visual element is, or will be,displayed. In response to determining the background color, the visualelement may be presented in another color that is different from thebackground color. The different color can provide human-discernablecontrast between the visual element and the background color to make iteasier for the user to see the visual element. In some cases, the colorof the visual element can be continuously, automatically, anddynamically adjusted, based on changes to the background color.

The user's location and movements can also be used to detect useractions that are categorized as indications of the user's intention tointeract (or not interact) with the electronic device. For example, theelectronic device may have access to a library (e.g., in a memorydevice) of actions that are categorized as indicators of a user's intentto interact or not interact with the device (e.g., reaching for theelectronic device, turning or walking toward or away from the electronicdevice, leaning toward or looking at the electronic device). In somecases, the electronic device may also include machine-learningtechnology that can add, remove, or modify the actions stored in thelibrary. Based on the detection of the user's presence, movements, andintention, the electronic device can cause the electronic device toenter and exit different modes of functionality and present differentvisual elements on a display, based on the modes. These modes can enabledifferent functionalities for the electronic device, and help the userunderstand the mode the electronic device is operating in, and theservices and functions that are available. FIGS. 13-15 illustrate theelectronic device operating in the multiple modes and describe examplesof the visual elements that can be presented on the display in thedifferent modes.

For instance, when the user is not detected near the electronic device(e.g., within the radar field 110 or the recognition zone), the deviceoperates in a dormant mode. In the dormant mode, the display (e.g., thedisplay 114) may present fewer visual elements than in other modes, orno visual elements and the display may be on or off. When the electronicdevice determines the presence of the user within the recognition zone(e.g., using radar data, or one or more subsets of the radar data, fromthe radar system 104), the electronic device exits the dormant mode andenters an aware mode. In the aware mode, the display presents one ormore visual elements that can indicate a status or functionality levelof the electronic device.

While the electronic device is in the aware mode, the electronic devicecan detect a user action that is categorized as an indication of a userintent to interact with the electronic device. In response to detectingthis user action, the electronic device can prepare an authenticationsystem to perform an authentication process. In some implementations,when the electronic device detects the indication of the user's intentto interact, the electronic device also exits the aware mode and entersan engaged mode. In the engaged mode, the display presents additional oralternate visual elements that can indicate changes in the status orfunctionality level of the electronic device. The electronic device canalso detect a trigger event and, based on the trigger event, cause theauthentication system to authenticate the user. In response to the userbeing authenticated, the electronic device exits the aware or engagedmode and enters an active mode. In the active mode, the display presentsadditional or alternate visual elements that can indicate changes in thestatus or functionality level of the electronic device.

FIG. 13 illustrates an example 1300 of an electronic devicetransitioning from the dormant mode to the aware mode. A detail view1300-1 shows the electronic device 102 in the dormant mode while a user1302 is outside of a recognition zone 1304. In this example, therecognition zone 1304 has a wedge shape, but as noted, the recognitionzone 1304 can take any suitable shape or size. Continuing the example,in this case the display 114 is not presenting any visual elements inthe dormant mode, as shown on an example display 114-22. In anotherdetail view 1300-2, the user 1302 is closer to the electronic device102, which has determined that the user 1302 has entered the recognitionzone 1304. Based on this determination, the electronic device 102 exitsthe dormant mode and enters the aware mode, as shown by an arrow 1306.

In the detail view 1300-2, multiple visual elements are presented on anexample display 114-23. For example, in the aware mode, the exampledisplay 114-23 presents a time-of-day element 1308 (a clock), a dateelement 1310, a connectivity status element 1312 (e.g., Wi-Fi, cellular,or other network connectivity), and a battery-level indicator element1314 (including a graphical element and a percentage indicator). In thedetail view 1300-2, the remainder of the example display 114-23 isblank. In some implementations, however, additional elements may bedisplayed, including a background image, such as a wallpaper or otherimage. Though not shown in FIG. 13, if the user 1302 exits therecognition zone 1304, the electronic device 102 may stop displaying thevisual elements and return to the dormant mode (immediately or after theuser 1302 has been outside the recognition zone 1304 for a selectablepredetermined amount of time).

FIG. 14 illustrates an example 1400 of an electronic devicetransitioning from the aware mode to the optional engaged mode. A detailview 1400-1 shows the user 1302 within the recognition zone 1304 and theelectronic device 102 in the aware mode, as described with reference toFIG. 13, including displaying multiple visual elements (1308, 1310,1312, 1314) on an example display 114-24. Another detail view 1400-2shows the user 1302 reaching for the electronic device 102. Theelectronic device 102 detects the reach (e.g., using one or more subsetsof the radar data) as a user action that is an indication of a userintent to interact with the electronic device 102. In response todetecting this user action indicating intent, the electronic device 102exits the aware mode and enters the engaged mode, as shown by an arrow1402.

In the detail view 1400-2, additional visual elements are presented onan example display 114-25. For example, in the engaged mode, the exampledisplay 114-25 presents a background image 1404 (in this case, an imageof the Golden Gate Bridge). The background image 1404 may have dynamicfeatures that adjust with the context of the user, such as animation, orvarying brightness or transparency levels that change depending on thedistance or speed of the reach. While in the engaged mode, theelectronic device 102 also prepares an authentication system to performan authentication process (note that in some cases, the electronicdevice 102 does not enter the engaged mode and instead prepares theauthentication system while in the aware mode, in response to the useraction that indicates user intent). Accordingly, the example display114-25 also presents a lock icon 1406, which indicates that full accessto the electronic device 102 is unavailable until the user 1302 isauthenticated. In some implementations, additional visual elements maybe displayed on the example display 114-25, and some or all of thevisual elements presented on the example display 114-24 may cease beingpresented. Though not shown in FIG. 14, if the user 1302 withdraws thereach gestures, the electronic device 102 may exit the engaged mode andreturn to the aware mode (immediately or after the reach has beenwithdrawn for a selectable predetermined amount of time).

FIG. 15 illustrates an example 1500 of an electronic devicetransitioning from the engaged mode to the active mode after the user1302 is authenticated (note that in some implementations, the electronicdevice can transition to the active mode from the aware mode). A detailview 1500-1 shows the user 1302 within the recognition zone 1304 and theelectronic device 102 in the engaged mode, as described with referenceto FIG. 14, including displaying multiple visual elements on an exampledisplay 114-26 (1308, 1310, 1312, 1314, 1404, 1406). As noted withreference to FIG. 14, when the user reaches for the electronic device102, the authentication system prepares to authenticate the user 1302.In FIG. 15, another detail view 1500-2 shows that the user 1302 haspicked up the electronic device 102. The electronic device 102determines that being picked up is a trigger event, as described above,and authenticates the user 1302. When the user 1302 is authenticated,the electronic device 102 exits the engaged mode (or the aware mode) andenters an active mode, as shown by an arrow 1502.

Additional visual elements associated with the active mode may also bepresented on an example display 114-27, as shown in the detail view1500-2. For example, in the active mode, the example display 114-27continues to present the visual elements associated with the aware mode,but the background image 1404 (associated with the engaged mode) haschanged to another background image 1504, a beach silhouette (note thatbecause the background image 1504 has a different color scheme, some ofthe visual elements have changed contrast or color so that they remainvisible to the user 1302). Additionally, the engaged mode lock icon 1406has transitioned to an unlock icon 1506, which indicates that the user1302 is authenticated. In some implementations, the unlock icon 1506 maybe presented for a duration of time and then fade. While not illustratedin FIG. 15, additional visual elements may be displayed on the exampledisplay 114-27 after the unlock icon 1506 fades, such as an instruction(e.g., “Swipe or tap to open”), one or more application launch icons, orother visual elements available to the electronic device 102.

In some implementations, the user 1302 may remain authenticated as longas the user 1302 remains within the recognition zone (e.g., therecognition zone 1304) or within another defined area within which theradar system can detect the presence of the user 1302. In theseimplementations, the display 114 may remain powered and able to receiveinput and present content, or the screen may turn off to save batterypower. Because the user 1302 remains authenticated, even if the screenis off, the user can access the electronic device 102 by touching thescreen, picking up the device, or another action, without having to bere-authenticated. In this way, the user's enjoyment and experience withthe electronic device 102 can be improved while preserving batterypower.

Further, the described progression between modes (e.g., from the dormantmode, through the aware and engaged modes, to authentication and theactive mode), may instead run in an opposite direction. For example,when the electronic device 102 is in the active mode and the user 1302sets it down (e.g., another trigger event occurs), the electronic devicemay enter a locked state (e.g., de-authenticate the user 1302), and/orplace the electronic device 102 in the engaged or aware mode, asdescribed above. Accordingly, if the user's hand remains near theelectronic device 102 (e.g., remains in a “reach” position), theelectronic device 102 may remain in the engaged mode. Conversely, if theuser's hand is withdrawn, the electronic device 102 may enter the awaremode. Then, as noted, the electronic device 102 may remain in the awaremode while the user is in the recognition zone. During this progressionbetween zones, the display 114 may present the visual elements describedabove for each zone, to indicate the changing status of the electronicdevice 102 to the user 1302.

As noted, in some implementations, applications running on theelectronic device 102 may be able to receive input through radar-basedtouch-independent gestures (radar gestures). In these cases, the radarsystem 104 may detect a reach by the user and perform actions, based onthe context of the electronic device 102. For example, when theelectronic device is in any of the modes described above, the user mayreceive a phone call, receive an alarm, alert, or notification, or playmusic through the electronic device. In these situations, the user mayreach toward the electronic device to respond to the action. Thus, areach may reduce or silence the ringer or notification during anincoming call or an alarm. Further, if the user notices an alert ornotification is being displayed, and reaches toward the electronicdevice, the notification may be dismissed or become interactive. Forexample, upon detecting the user's reach, the electronic device maydisplay the notification in a mode that allows the user to respond bydismissing or postponing the alert/notification, replying (in the caseof a message or email notification), or in another manner. In somecases, the displayed notification may change color or size as well. Inthe example of the user listening to music, a reach may cause theelectronic device to present a control screen for the music player, sothat the user can control the track, volume, or other parameter.

Some or all of these features may be available in different modes, andwhich features are available may be user-selectable. For example, theuser may allow volume silencing and music control in all modes but allowresponding to alerts and notifications only in the active mode (e.g.,when the user has been authenticated and has not left the recognitionzone). Other combinations of features and permission levels may also beselected by the user.

Among the advantages of the described implementations, includingimplementations in which radar sensing is used to detect the presence ofthe user within a recognition zone, and further includingimplementations in which radar is used to detect user action that iscategorized as an indication of a user intent to interact with theelectronic device, either of which might alternatively be achievableusing the on-device camera that is provided with most modernsmartphones, is that the power usage of the radar facility issubstantially less than the power usage of the camera facility, whilethe propriety of the results can often be better with the radar facilitythan with the camera facility. For example, using the radar facilitydescribed hereinabove, the desired user-state or user-intentiondetection can be achieved at average power ranging from single-digitmilliwatts to just a few dozen milliwatts (e.g., 10 mW, 20 mW, 30 mW or40 mW), even including the processing power for processing the radarvector data to make the determinations. At these low levels of power, itwould be readily acceptable to have the radar facility in an always-onstate. As such, for example, with the smartphone radar facility in thealways-on state, the desired delightful and seamless experiencepresently described can still be provided for a user that has beensitting across the room from their smartphone for many hours.

In contrast, the optical cameras provided with most of today'ssmartphones typically operate at hundreds of milliwatts of power (e.g.,an order of magnitude higher than 40 mW, which is 400 mW). At such powerrates, optical cameras would be disadvantageous because they wouldsignificantly reduce the battery life of most of today's smartphones, somuch so as to make it highly impractical, if not prohibitive, to havethe optical camera in an always-on state. An additional advantage of theradar facility is that the field of view can be quite large, readilyenough to detect a user walking up from any direction even when lyingflat and face-up on a table (for many typical implementations in whichthe radar chip is facing outward in the same general direction as theselfie camera) and, furthermore, by virtue of its Doppler processingability can be highly effective (especially at operating frequenciesnear 60 GHz) in detecting even relatively subtle movements of movingbodies from the variety of directions.

Additionally, the radar facility can operate in environments in whichthe performance of the camera facility is reduced or restricted. Forexample, in lower-light environments, the camera facility may have areduced ability to detect shape or movement. In contrast, the radarfacility performs as well in lower-light as in full light. The radarfacility can also detect presence and gestures through some obstacles.For instance, if the smartphone is in a pocket or a jacket or pair ofpants, a camera facility cannot detect a user or a gesture. The radarfacility, however, can still detect objects in its field, even through afabric that would block the camera facility. An even further advantageof using a radar facility over an onboard video camera facility of asmartphone is privacy, because a user can have the advantages of theherein described delightful and seamless experiences while at the sametime not needing to be worried that there is a video camera taking videoof them for such purposes.

Example Computing System

FIG. 16 illustrates various components of an example computing system1600 that can be implemented as any type of client, server, and/orelectronic device as described with reference to the previous FIGS. 1-15to implement input methods for mobile devices.

The computing system 1600 includes communication devices 1602 thatenable wired and/or wireless communication of device data 1604 (e.g.,radar data, authentication data, reference data, received data, datathat is being received, data scheduled for broadcast, and data packetsof the data). The device data 1604 or other device content can includeconfiguration settings of the device, media content stored on thedevice, and/or information associated with a user of the device (e.g.,an identity of a person within a radar field or customized gesturedata). Media content stored on the computing system 1600 can include anytype of radar, biometric, audio, video, and/or image data. The computingsystem 1600 includes one or more data inputs 1606 via which any type ofdata, media content, and/or inputs can be received, such as humanutterances, interactions with a radar field (e.g., a radar gesture),touch inputs, user-selectable inputs or interactions (explicit orimplicit), messages, music, television media content, recorded videocontent, and any other type of audio, video, and/or image data receivedfrom any content and/or data source.

The computing system 1600 also includes communication interfaces 1608,which can be implemented as any one or more of a serial and/or aparallel interface, a wireless interface, any type of network interface,a modem, and as any other type of communication interface. Thecommunication interfaces 1608 provide a connection and/or communicationlinks between the computing system 1600 and a communication network bywhich other electronic, computing, and communication devices communicatedata with the computing system 1600.

The computing system 1600 includes one or more processors 1610 (e.g.,any of microprocessors, controllers, or other controllers) that canprocess various computer-executable instructions to control theoperation of the computing system 1600 and to enable techniques for, orin which can be implemented, the input methods for mobile devices.Alternatively or additionally, the computing system 1600 can beimplemented with any one or combination of hardware, firmware, or fixedlogic circuitry that is implemented in connection with processing andcontrol circuits, which are generally identified at 1612. Although notshown, the computing system 1600 can include a system bus or datatransfer system that couples the various components within the device.The system bus can include any one or combination of different busstructures, such as a memory bus or memory controller, a peripheral bus,a universal serial bus, and/or a processor or local bus that utilizesany of a variety of bus architectures. Also not shown, the computingsystem 1600 can include one or more non-radar sensors, such as thenon-radar sensors 108.

The computing system 1600 also includes computer-readable media 1614,such as one or more memory devices that enable persistent and/ornon-transitory data storage (e.g., in contrast to mere signaltransmission), examples of which include random access memory (RAM),non-volatile memory (e.g., any one or more of a read-only memory (ROM),flash memory, EPROM, EEPROM, etc.), and a disk storage device. A diskstorage device may be implemented as any type of magnetic or opticalstorage device, such as a hard disk drive, a recordable and/orrewriteable compact disc (CD), any type of a digital versatile disc(DVD), and the like. The computing system 1600 can also include a massstorage media device (storage media) 1616.

The computer-readable media 1614 provides data storage mechanisms tostore the device data 1604, as well as various device applications 1618and any other types of information and/or data related to operationalaspects of the computing system 1600. For example, an operating system1620 can be maintained as a computer application with thecomputer-readable media 1614 and executed on the processors 1610. Thedevice applications 1618 may include a device manager, such as any formof a control application, software application, signal-processing andcontrol modules, code that is native to a particular device, anabstraction module, a gesture recognition module, and/or other modules.The device applications 1618 may also include system components,engines, modules, or managers to implement the input methods for mobiledevices, such as the radar system 104, the interaction manager 106, orthe application manager 116. The computing system 1600 may also include,or have access to, one or more machine-learning systems.

Several examples are described below.

Example 1: A method implemented in an electronic device that includes adisplay and a radar system, the method comprising: determining, based onradar data received through the radar system, that a portion of a useris within a gesture zone of the electronic device; determining that anapplication operating on the electronic device is configured to receiveradar-gesture input, the radar-gesture input determined from radar datathat is generated by the radar system; and responsive to thedetermination that the portion of the user is within the gesture zone ofthe electronic device and the determination that the applicationoperating on the electronic device is configured to receiveradar-gesture input, providing a feedback indicator on the display ofthe electronic device, the providing of the feedback indicatorindicating that: the portion of the user is within the gesture zone; andthe application can receive the radar-gesture input.

Example 2: The method of example 1, wherein the feedback indicator is avisual element that appears at an edge of an active area of the display.

Example 3: The method of example 2, wherein the visual element includes:an area that comprises a portion of the active area of the display; avisual property, the visual property comprising a luminosity, a color, acontrast, a shape, a saturation, and/or an opaqueness that is differentfrom the visual property of another portion of the display that isproximate to the visual element; and a segment of an exterior borderthat is within a threshold distance of the edge of the active area ofthe display.

Example 4: The method of example 3, wherein the visual property of thevisual element varies across the area of the visual element.

Example 5: The method of any of examples 1-4, wherein: the portion ofthe user that is within the gesture zone is a hand of the user; anddetermining that the portion of the user is within the gesture zone ofthe electronic device comprises detecting a reach, by the hand of theuser, toward the electronic device.

Example 6: The method of example 1, wherein: providing the feedbackindicator on the display of the electronic device comprises adjusting avisual element that was previously presented on the display, thepreviously presented visual element indicating that the applicationoperating on the electronic device is configured to receiveradar-gesture input and appearing at an edge of the active area of thedisplay; and adjusting the previously presented visual element comprisesenlarging an area of the previously presented visual element.

Example 7: The method of example 6, wherein enlarging the area of thepreviously presented visual element comprises: extending the previouslypresented visual element in a direction parallel to the edge of theactive area of the display; or extending the previously presented visualelement in a direction away from the edge of the active area of thedisplay.

Example 8: The method of any of examples 1-7, further comprisingdynamically adjusting a visual property of the feedback indicatorcorresponding to a distance of the user in the gesture zone from theelectronic device and/or a movement of the portion of the user in thegesture zone.

Example 9: The method of example 8, wherein: the visual property is atleast one of a luminosity, a brightness, or a visual intensity of thefeedback indicator; a measurement of the visual property increases asthe distance approaches an amount corresponding to an improvedradar-gesture-recognition efficacy of the radar system; and ameasurement of the visual property of the feedback indicator decreasesas the distance approaches an amount corresponding to a reducedradar-gesture-recognition efficacy.

Example 10: The method of any of examples 1-9, further comprisingdynamically adjusting a position of the feedback indicator on thedisplay, the dynamic adjustment of the feedback indicator correspondingto movement of the portion of the user that is within the gesture zoneof the electronic device, the movement of the portion of the user thatis within the gesture zone of the electronic device based on a firstsubset of the radar data on which the determination that the portion ofthe user is within the gesture zone of the electronic device was basedor on a second subset of the radar data, the second subset of the radardata received, by the radar system, after reception of the first subsetof the radar data.

Example 11. The method of any of examples 1-10, further comprising:determining, based on a first subset of the radar data on which thedetermination that the portion of the user is within the gesture zone ofthe electronic device was based or on a second subset of the radar data,the second subset of the radar data received, by the radar system, afterreception of the first subset of the radar data, that the portion of theuser is no longer within the gesture zone; and responsive to thedetermination that the portion of the user is no longer within thegesture zone, ceasing to provide the feedback indicator on the displayof the electronic device.

Example 12: The method of any of examples 1-11, further comprising:determining a background color of a region of the display on which thefeedback indicator is displayed; and responsive to determining thebackground color of the region of the display on which the feedbackindicator is displayed, causing the display to provide the feedbackindicator in another color that is different from the background color,the different color effective to provide human-discernable contrastbetween the feedback indicator and the region of the display on whichthe feedback indicator is displayed.

Example 13: An electronic device comprising: a display; a radar system,implemented at least partially in hardware, configured to: provide aradar field; sense reflections from a user in the radar field; analyzethe reflections from the user in the radar field; and provide, based onthe analysis of the reflections, radar data; a computer processor; and acomputer-readable media having instructions stored thereon that,responsive to execution by the computer processor, implement aradar-based interaction manager configured to: determine that anapplication operating on the electronic device is configured to receiveradar-gesture input; determine, based on the radar data, that a portionof the user is within a gesture zone of the electronic device; andresponsive to the determination that the application operating on theelectronic device is configured to receive radar-gesture input and thedetermination that the portion of the user is within the gesture zone ofthe electronic device, cause the display to present a feedbackindicator, the presentation of the feedback indicator indicating that:the portion of the user is within the gesture zone; and the applicationcan receive the radar-gesture input.

Example 14: The electronic device of example 13, wherein the feedbackindicator is a visual element that appears at an edge of an active areaof the display.

Example 15: The electronic device of example 14, wherein the visualelement includes: an area that comprises a portion of the active area ofthe display; a visual property, the visual property comprising aluminosity, a color, a contrast, a shape, a saturation, and/or anopaqueness that is different from the visual property of another portionof the display that is proximate to the visual element; and a segment ofan exterior border that is within a threshold distance of the edge ofthe active area of the display.

Example 16: The electronic device of example 15, wherein the visualproperty of the visual element varies across the area of the visualelement.

Example 17: The electronic device of any of examples 13-16, wherein: theportion of the user that is within the gesture zone is a hand of theuser; and the determination of the portion of the user within thegesture zone of the electronic device is a determination of a reach, bythe hand of the user, toward the electronic device.

Example 18: The electronic device of example 13, wherein: to cause thedisplay to present the feedback indicator comprises to cause the displayto make an adjustment to a previously presented visual element, thepreviously presented visual element indicating that the applicationoperating on the electronic device is configured to receiveradar-gesture input and appearing at an edge of the active area of thedisplay; and the adjustment to the previously presented visual elementcomprises at least enlarging an area of the previously presented visualelement.

Example 19: The electronic device of example 18, wherein enlarging thearea of the previously presented visual element comprises: extending thepreviously presented visual element in a direction parallel to the edgeof the active area of the display; or extending the previously presentedvisual element in a direction away from the edge of the active area ofthe display.

Example 20: The electronic device of any examples 13-19, wherein theradar-based interaction manager is further configured to dynamicallyadjust a visual property of the feedback indicator corresponding to adistance of the portion of the user in the gesture zone from theelectronic device or a movement of the portion of the user in thegesture zone.

Example 21: The electronic device of example 20, wherein the visualproperty is at least one of a luminosity, a brightness, or a visualintensity of the feedback indicator; a measurement of the visualproperty increases as the distance approaches an amount corresponding toan improved radar-gesture-recognition efficacy of the radar system; anda measurement of the visual property of the feedback indicator decreasesas the distance approaches an amount corresponding to a reducedradar-gesture-recognition efficacy.

Example 22: The electronic device of any of examples 13-21, wherein theradar-based interaction manager is further configured to dynamicallyadjust a position of the feedback indicator on the display, the dynamicadjustment of the feedback indicator corresponding to movement of theportion of the user that is within the gesture zone of the electronicdevice, the movement of the portion of the user that is within thegesture zone of the electronic device based on a first subset of theradar data on which the determination that the portion of the user iswithin the gesture zone of the electronic device was based or a secondsubset of the radar data, the second subset of the radar data received,by the radar system, after reception of the first subset of the radardata.

Example 23: The electronic device of any of examples 13-22, wherein theradar-based interaction manager is further configured to: determine,based on a first subset of the radar data on which the determinationthat the portion of the user is within the gesture zone of theelectronic device was based or on a second subset of the radar data, thesecond subset of the radar data received, by the radar system, afterreception of the first subset of the radar data, that the portion of theuser is no longer within the gesture zone; and responsive to thedetermination that the portion of the user is no longer within thegesture zone, cause the display to cease to present the feedbackindicator.

Example 24: The electronic device of any of examples 13-23, wherein theradar-based interaction manager is further configured to: determine abackground color of a region of the display on which the feedbackindicator is presented; and responsive to the determination of thebackground color of the region of the display on which the feedbackindicator is displayed, cause the display to present the feedbackindicator in another color that is different from the background color,the different color effective to provide human-discernable contrastbetween the feedback indicator and the region of the display on whichthe feedback indicator is displayed.

CONCLUSION

Although implementations of techniques for, and apparatuses enabling,input methods for mobile devices have been described in languagespecific to features and/or methods, it is to be understood that thesubject of the appended claims is not necessarily limited to thespecific features or methods described. Rather, the specific featuresand methods are disclosed as example implementations enabling the inputmethods for mobile devices.

1. A method implemented in an electronic device that includes a displayand a radar system, the method comprising: determining, based on radardata received through the radar system, that a portion of a user iswithin a gesture zone of the electronic device; determining that anapplication operating on the electronic device is configured to receiveradar-gesture input; and responsive to the determination that theportion of the user is within the gesture zone of the electronic deviceand the determination that the application operating on the electronicdevice is configured to receive radar-gesture input, enlarging an areaof a visual element that was previously presented on the display, thepreviously-presented visual element: indicating that the portion of theuser is within the gesture zone and the application is configured toreceive the radar-gesture input; and appearing at an edge of an activearea of the display.
 2. (canceled)
 3. The method of claim 1, wherein thepreviously-presented visual element includes: an area that comprises aportion of the active area of the display; a visual property, the visualproperty comprising a luminosity, a color, a contrast, a shape, asaturation, or an opaqueness that is different from the visual propertyof another portion of the display that is proximate to thepreviously-presented visual element; and a segment of an exterior borderthat is within a threshold distance of the edge of the active area ofthe display.
 4. The method of claim 3, wherein the visual property ofthe previously-presented visual element varies across the area of thepreviously-presented visual element.
 5. The method of claim 1, wherein:the portion of the user that is within the gesture zone is a hand of theuser; and determining that the portion of the user within the gesturezone of the electronic device comprises detecting a reach, by the handof the user, toward the electronic device.
 6. (canceled)
 7. The methodof claim 1, wherein enlarging the area of the previously-presentedvisual element comprises: extending the previously-presented visualelement in a direction parallel to the edge of the active area of thedisplay; or extending the previously-presented visual element in adirection away from the edge of the active area of the display.
 8. Themethod of claim 1, further comprising: dynamically adjusting a visualproperty of the previously-presented visual element corresponding to adistance of the portion of the user in the gesture zone from theelectronic device or a movement of the portion of the user in thegesture zone.
 9. The method of claim 8, wherein: the visual property isat least one of a luminosity, a brightness, or a visual intensity of thepreviously-presented visual element; a measurement of the visualproperty increases as the distance approaches an amount corresponding toan improved radar-gesture-recognition efficacy of the radar system; anda measurement of the visual property of the previously-presented visualelement decreases as the distance approaches an amount corresponding toa reduced radar-gesture-recognition efficacy.
 10. The method of claim 1,further comprising dynamically adjusting a position of thepreviously-presented visual element on the display, the dynamicadjustment of the previously-presented visual element corresponding tomovement of the portion of the user that is within the gesture zone ofthe electronic device, the movement of the portion of the user that iswithin the gesture zone of the electronic device based on a first subsetof the radar data on which the determination that the portion of theuser is within the gesture zone of the electronic device was based or ona second subset of the radar data, the second subset of the radar datareceived, by the radar system, after reception of the first subset ofthe radar data.
 11. The method of claim 1, further comprising:determining, based on a first subset of the radar data on which thedetermination that the portion of the user is within the gesture zone ofthe electronic device was based or on a second subset of the radar data,the second subset of the radar data received, by the radar system, afterreception of the first subset of the radar data, that the portion of theuser is no longer within the gesture zone; and responsive to thedetermination that the portion of the user is no longer within thegesture zone, ceasing to enlarge the area of the previously-presentedvisual element.
 12. The method of claim 1, further comprising:determining a background color of a region of the display on which thepreviously-presented visual element is displayed; and responsive todetermining the background color of the region of the display on whichthe previously-presented visual element is displayed, causing thedisplay to provide the previously-presented visual element in anothercolor that is different from the background color, the different coloreffective to provide human-discernable contrast between thepreviously-presented visual element and the region of the display onwhich the previously-presented visual element is displayed.
 13. Anelectronic device comprising: a display; a radar system, implemented atleast partially in hardware, configured to: provide a radar field; sensereflections from a user in the radar field; analyze the reflections fromthe user in the radar field; and provide, based on the analysis of thereflections, radar data; a computer processor; and a computer-readablemedia having instructions stored thereon that, responsive to executionby the computer processor, implement a radar-based interaction managerconfigured to: determine that an application operating on the electronicdevice is configured to receive radar-gesture input; determine, based onthe radar data, that a portion of the user is within a gesture zone ofthe electronic device; and responsive to the determination that theapplication operating on the electronic device is configured to receiveradar-gesture input and the determination that the portion of the useris within the gesture zone of the electronic device, cause the displayto enlarge an area of a visual element that was previously presented onthe display, the previously-presented visual element: indicating thatthe portion of the user is within the gesture zone and the applicationis configured to receive the radar-gesture input and appearing at anedge of an active area of the display.
 14. (canceled)
 15. The electronicdevice of claim 13, wherein the previously-presented visual elementincludes: an area that comprises a portion of the active area of thedisplay; a visual property, the visual property comprising a luminosity,a color, a contrast, a shape, a saturation, or an opaqueness that isdifferent from the visual property of another portion of the displaythat is proximate to the previously-presented visual element; and asegment of an exterior border that is within a threshold distance of theedge of the active area of the display.
 16. The electronic device ofclaim 15, wherein the visual property of the previously-presented visualelement varies across the area of the previously-presented visualelement.
 17. The electronic device of claim 13, wherein: the portion ofthe user that is within the gesture zone is a hand of the user; and thedetermination of the portion of the user within the gesture zone of theelectronic device is a determination of a reach, by the hand of theuser, toward the electronic device.
 18. (canceled)
 19. The electronicdevice of claim 13, wherein enlarging the area of thepreviously-presented visual element comprises: extending thepreviously-presented visual element in a direction parallel to the edgeof the active area of the display; or extending the previously-presentedvisual element in a direction away from the edge of the active area ofthe display.
 20. The electronic device of claim 13, wherein theradar-based interaction manager is further configured to dynamicallyadjust a visual property of the previously-presented visual elementcorresponding to a distance of the portion of the user in the gesturezone from the electronic device or a movement of the portion of the userin the gesture zone.
 21. The electronic device of claim 20, wherein: thevisual property is at least one of a luminosity, a brightness, or avisual intensity of the previously-presented visual element; ameasurement of the visual property increases as the distance approachesan amount corresponding to an improved radar-gesture-recognitionefficacy of the radar system; and a measurement of the visual propertyof the previously-presented visual element decreases as the distanceapproaches an amount corresponding to a reducedradar-gesture-recognition efficacy.
 22. The electronic device of claim13, wherein the radar-based interaction manager is further configured todynamically adjust a position of the previously-presented visual elementon the display, the dynamic adjustment of the previously-presentedvisual element corresponding to movement of the portion of the user thatis within the gesture zone of the electronic device, the movement of theportion of the user that is within the gesture zone of the electronicdevice based on a first subset of the radar data on which thedetermination that the portion of the user is within the gesture zone ofthe electronic device was based or a second subset of the radar data,the second subset of the radar data received, by the radar system, afterreception of the first subset of the radar data.
 23. The electronicdevice of claim 13, wherein the radar-based interaction manager isfurther configured to: determine, based on a first subset of the radardata on which the determination that the portion of the user is withinthe gesture zone of the electronic device was based or on a secondsubset of the radar data, the second subset of the radar data received,by the radar system, after reception of the first subset of the radardata, that the portion of the user is no longer within the gesture zone;and responsive to the determination that the portion of the user is nolonger within the gesture zone, cause the display to cease to enlargethe area of the previously-presented visual element.
 24. The electronicdevice of claim 13, wherein the radar-based interaction manager isfurther configured to: determine a background color of a region of thedisplay on which the previously-presented visual element is presented;and responsive to the determination of the background color of theregion of the display on which the previously-presented visual elementis displayed, cause the display to present the previously-presentedvisual element in another color that is different from the backgroundcolor, the different color effective to provide human-discernablecontrast between the previously-presented visual element and the regionof the display on which the previously-presented visual element isdisplayed.